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1.
C.V. Cole J. Duxbury J. Freney O. Heinemeyer K. Minami A. Mosier K. Paustian N. Rosenberg N. Sampson D. Sauerbeck Q. Zhao 《Nutrient Cycling in Agroecosystems》1997,49(1-3):221-228
Technologies to reduce net emissions of carbon dioxide, methane and nitrous oxide within the agriculture sector were reviewed
to estimate the global potential for mitigation of these radiatively active greenhouse gases. Our estimates of the potential
reduction of radiative forcing by the agricultural sector range from 1.15-3.3 Gt C equivalents per year. Of the total potential
reduction, approximately 32% could result from reduction in CO2 emissions, 42% of carbon offsets by biofuel production on 15% of existing croplands, 16% from reduced CH4 emissions and 10% from reduced emissions of N2O. Agriculture encompasses large regional differences in management practices and rates of potential adoption of mitigation
practices. Acceptability of mitigation options will depend on the extent to which sustainable production will be achieved
or maintained and benefits will accrue to farmers. Technologies such as no-till farming and strategic fertilizer placement
and timing are now being adopted for reasons other than concern for climate change issues.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
Technical and policy aspects of strategies to decrease greenhouse gas emissions from agriculture 总被引:4,自引:0,他引:4
Agricultural activities greatly contribute to the global net flux of CH4, N2O and CO2 from the terrestrial biosphere into the atmosphere. For CH4 and N2O, the net contribution is in the order of 40%. Because of this relatively large contribution, there is an urgent need for
the implementation of effective strategies to decrease the net flux of CH4, N2O and CO2 from agriculture. The objectives of this paper are to review the various measures that have been proposed so far and to discuss
the constraints and challenges. A large number of suggestions for decreasing emissions of CH4, N2O and CO2 from agriculture can be found in literature. Common to most of these abatement measures is that the suggested potentials
to decrease the emissions of CO2, CH4 and N2O from agriculture are large. Common to most of the measures is also the `single gas' and `source-oriented' approach. In most
papers it has been implicitly assumed that farmers are able and willing to implement the proposed measures. So far, none of
the measures has been consciously implemented and tested at farm scale. The major challenge of policy makers is to formulate
effective and efficient policies and measures, using the potentials of the abatement measures proposed so far, and in an international
setting with still highly uncertain cause–effect relationships. Major constraints for policy makers follow from the complexities
and possible feed back and side effects of abatement measures, from the many stakeholders involved, often with contrasting
views, and from the unfamiliarity of farmers with the problem of climate change. Because of the many complexities and interactions
involved, policy makers should follow two tracks. Priority should be given to chain-oriented measures, i.e. measures that
aim at an increased carbon, nitrogen and water use efficiencies in the whole food chain, above source-oriented measures, i.e.
measures that aim at decreased emission from specific sources. Chain-oriented measures should fit in with other environmental
policies that aim at increasing resource use efficiency, to be effective and efficient.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
Hope W. Phetteplace Donald E. Johnson Andrew F. Seidl 《Nutrient Cycling in Agroecosystems》2001,60(1-3):99-102
Computer spreadsheets were developed to evaluate greenhouse gas (GHG) emissions from U.S. beef and dairy livestock systems
from nine locations. Of the beef systems the cow-calf herd emitted the most and feedlot cattle the least methane (CH4) and nitrous oxide (N2O) per unit product. Carbon dioxide (CO2) emissions per unit product were the least for the cow-calf and greatest for the feedlot scenarios. In the dairy systems
approximately one-half of the total GHG CO2 equivalents were from CH4 and one-third from N2O. Mitigation strategies, such as intensive grazing, reduced GHG emissions by approximately 10%.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
The significance of agricultural sources of greenhouse gases 总被引:17,自引:0,他引:17
John M. Duxbury 《Nutrient Cycling in Agroecosystems》1994,38(2):151-163
The impact of development of land for agriculture and agricultural production practices on emissions of greenhouse gases is reviewed and evaluated within the context of anthropogenic radiative forcing of climate. Combined, these activities are estimated to contribute about 25%, 65%, and 90% of total anthropogenic emissions of CO2, CH4, and N2O, respectively. Agriculture is also a significant contributor to global emissions of NH3, CO, and NO. Over the last 150 y, cumulative emissions of CO2 associated with land clearing for agriculture are comparable to those from combustion of fossil fuel, but the latter is the major source of CO2 at present and is projected to become more dominant in the future. Ruminant animals, rice paddies, and biomass burning are principal agricultural sources of CH4, and oxidation of CH4 by aerobic soils has been reduced by perturbations to natural N cycles. Agricultural sources of N2O have probably been substantially underestimated due to incomplete analysis of increased N flows in the environment, especially via NH3 volatilization from animal manures, leaching of NO
3
-
, and increased use of biological N fixation.The contribution of agriculture to radiative forcing of climate is analyzed using data from the Intergovernmental Panel on Climate Change (IPCC)(base case) and cases where the global warming potential of CH4, and agricultural emissions of N2O are doubled. With these scenarios, agriculture, including land clearing, is estimated to contribute between 28–33% of the radiative forcing created over the next 100yr by 1990 anthropogenic emissions of CO2, CH4, and N2O. Analyses of the sources of agriculturally generated radiative climate forcing show that 80% is associated with tropical agriculture and that two-thirds comes from non-soil sources of greenhouse gases. The importance of agriculture to radiative forcing created by different countries varies widely and is illustrated by comparisons between the USA, India, and Brazil. Some caveats to these analyses include inadequate evaluations of the net greenhouse effects of agroecosystems, uncertainties in global fluxes of greenhouse gases, and incomplete understanding of tropospheric chemical processes.Extension of the analytical approach to projected future emissions of greenhouse gases (IPCC moderate growth scenario) indicates that agriculture will become a less important source of radiative forcing in the future. Technological approaches to mitigation of agricultural sources of greenhouse gases will probably focus on CH4 and N2O because emissions of CO2 are essentially associated with the socio-political issue of tropical deforestation. Available technologies include dietary supplements to reduce CH4 production by ruminant animals and various means of improving fertilizer N management to reduce N2O emissions. Increased storage of C in soil organic matter is not considered to be viable because of slow accretion rates and misconceptions about losses of soil organic matter from agricultural soils. 相似文献
5.
Jørgen E. Olesen Gitte H. Rubæk Tove Heidmann Søren Hansen Christen D. Børgensen 《Nutrient Cycling in Agroecosystems》2004,70(2):147-160
The DAISY soil–plant–atmosphere model was used to simulate crop production and soil carbon (C) and nitrogen (N) turnover for three arable crop rotations on a loamy sand in Denmark under varying temperature, rainfall, atmospheric CO2 concentration and N fertilization. The crop rotations varied in proportion of spring sown crops and use of N catch crops (ryegrass).
The effects on CO2 emissions were estimated from simulated changes in soil C. The effects on N2O emissions were estimated using the IPCC methodology from simulated amounts of N in crop residues and N leaching. Simulations were carried out using the original and a revised parameterization of the soil C turnover. The use of the revised model parameterization increased
the soil C and N turnover in the topsoil under baseline conditions, resulting in an increase in crop N uptake of 11 kg N ha–1 y–1 in a crop rotation with winter cereals and a reduction of 16 kg N ha–1 y–1 in a crop rotation with spring cereals and catch crops.
The effect of increased temperature, rainfall and CO2 concentration on N flows was of the same magnitude for both model parameterizations. Higher temperature and rainfall increased N leaching in all crop rotations, whereas effects on N in crop residues depended on use of catch crops. The total greenhouse gas (GHG) emission increased with increasing temperature. The increase in total GHG
emission was 66–234 kg CO2-eq ha–1 y–1 for a temperature increase of 4°C. Higher rainfall increased total GHG emissions most in the winter cereal dominated rotation. An increase in rainfall of 20% increased total GHG emissions by 11–53 kg CO2-eq ha–1
y–1, and a 50% increase in atmospheric CO2 concentration decreased emissions by 180–269 kg CO2-eq ha–1 y–1. The total GHG emissions increased considerably with increasing N fertilizer rate for a crop rotation with winter
cereals, but remained unchanged for a crop rotation with spring cereals and catch crops. The simulated increase in GHG emissions with global warming can be effectively mitigated by including more spring cereals and catch crops in the rotation. 相似文献
6.
Processes involving biomass oxidation are considered to be CO2 neutral since the replenishing of the biomass by normal growth will remove CO2 from the atmosphere. Thus the use of charcoal in the production of metallurgical coke, to be used as a reducing agent in the formation of iron, would be a strategy for the reduction of CO2 in the overall ironmaking process. This paper describes experimental attempts to produce industrial grade coke from coking coal blends to which are added amounts of charcoal up to 10%. Coking experiments were carried out partly in a 30 lb coke oven and partly in a sole heated oven. The influence of blend composition, heating rates and charcoal particle size was investigated. Cokes made using fine charcoal addition (− 60 mesh) were considerably weaker than cokes made from the base blend. This is interpreted to be the effect of the ash constituents in the charcoal which, among other things, contains much higher calcium than the coals used. However, carefully sized fractions of coarse charcoal (− 3/8 + 1/4 in) produced much higher quality coke, possibly the result of a different dispersion of the charcoal mineral components. 相似文献
7.
Enhancing the carbon sink in European agricultural soils: including trace gas fluxes in estimates of carbon mitigation potential 总被引:7,自引:0,他引:7
Pete Smith Keith W. Goulding Keith A. Smith David S. Powlson Jo U. Smith Pete Falloon Kevin Coleman 《Nutrient Cycling in Agroecosystems》2001,60(1-3):237-252
The possibility that the carbon sink in agricultural soils can be enhanced has taken on great political significance since
the Kyoto Protocol was finalised in December 1997. The Kyoto Protocol allows carbon emissions to be offset by demonstrable
removal of carbon from the atmosphere. Thus, forestry activities (Article 3.3) and changes in the use of agricultural soils
(Article 3.4) that are shown to reduce atmospheric CO2levels may be included in the Kyoto emission reduction targets. The European Union is committed to a reduction in CO2 emissions to 92% of baseline (1990) levels during the first commitment period (2008–2012). We have shown recently that there
are a number of agricultural land-management changes that show some potential to increase the carbon sink in agricultural
soils and others that allow alternative forms of carbon mitigation (i.e. through fossil fuel substitution), but the options
differ greatly in their potential for carbon mitigation. The changes examined were, (a) switching all animal manure use to
arable land, (b) applying all sewage sludge to arable land, (c) incorporating all surplus cereal straw, (d) conversion to
no-till agriculture, (e) use of surplus arable land to de-intensify 1/3 of current intensive crop production (through use
of 1/3 grass/arable rotations), (f) use of surplus arable land to allow natural woodland regeneration, and (g) use of surplus
arable land for bioenergy crop production. In this paper, we attempt for the first time to assess other (non-CO2) effects of these land-management changes on (a) the emission of the other important agricultural greenhouse gases, methane
and nitrous oxide, and (b) other aspects of the ecology of the agroecosystems. We find that the relative importance of trace
gas fluxes varies enormously among the scenarios. In some such as the sewage sludge, woodland regeneration and bioenergy production
scenarios, the inclusion of trace gases makes only a small (<10%) difference to the CO2-C mitigation potential. In other cases, for example the no-till, animal manure and agricultural de-intensification scenarios,
trace gases have a large impact, sometimes halving or more than doubling the CO2-C mitigation potential. The scenarios showing the greatest increase when including trace gases are those in which manure
management changes significantly. In the one scenario (no-till) where the carbon mitigation potential was reduced greatly,
a small increase in methane oxidation was outweighed by a sharp increase in N2O emissions. When these land-management options are combined to examine the whole agricultural land area of Europe, most of
the changes in mitigation potential are small, but depending upon assumptions for the animal manure scenario, the total mitigation
potential either increases by about 20% or decreases by about 10%, shifting the mitigation potential of the scenario from
just above the EU's 8% Kyoto emission reduction target (98.9 Tg C y−1) to just below it. Our results suggest that (a) trace gas fluxes may change the mitigation potential of a land management
option significantly and should always be considered alongside CO2-C mitigation potentials and (b) agricultural management options show considerable potential for carbon mitigation even after
accounting for trace gas fluxes.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
Xiying Hao 《Nutrient Cycling in Agroecosystems》2007,78(2):189-195
Greenhouse gases (CO2, CH4 and N2O) are emitted during livestock manure handling, including composting, storage and land application. However, published data
on emission rates of these gases during storage are sparse. In this study, the levels of GHG emissions and N levels during
compost storage were investigated. The compost materials were produced by composting livestock manure for 133 d with 0, 10,
20 and 30% phosphogypsum (PG) or 10, 20 and 30% sand amendment. These compost materials were then stored on a clay pad for
233 d. Results from this study indicated that TN content did not change but mineral N content increased significantly during
the 233 d storage for all treatments. The higher mineral N content in compost increases its agronomic value. There were only
trace amounts of CH4 and N2O emissions. The C loss during storage was mainly as CO2 and accounted for about 2.9 to 10% of total C initially in the compost. This information is vital to livestock manure life
cycle analysis, and can be used to develop best manure management strategies that reduce GHG emissions from livestock production.
The LRC Contribution No. 387-06006. 相似文献
9.
CaO-based sorbent looping cycle, i.e. cyclic calcination/carbonation, is one of the most interesting technologies for CO2 capture during coal combustion and gasification processes. In order to improve the durability of limestone during the multiple calcination/carbonation cycles, modified limestone with acetic acid solution was proposed as an CO2 sorbent. The cyclic carbonation conversions of modified limestone and original one were investigated in a twin fixed bed reactor system. The modified limestone shows the optimum carbonation conversion at the carbonation temperature of 650 °C and achieves a conversion of 0.5 after 20 cycles. The original limestone exhibits the maximum carbonation conversion of 0.15 after 20 cycles. Conversion of the modified limestone decreases slightly as the calcination temperature increases from 920 °C to 1100 °C with the number of cycles, while conversion of the original one displays a sharp decay at the same reaction conditions. The durability of the modified limestone is significantly better than the original one during the multiple cycles because mean grain size of CaO derived from the modified limestone is lower than that from the original one at the same reaction conditions. The calcined modified limestone shows higher surface area and pore volume than the calcined original one with the number of cycles, and pore size distribution of the modified limestone is superior to the original one after the same number of calcinations. 相似文献
10.
Agricultural soils emit nitrous oxide (N2O), a potent greenhouse gas. Predicting and mitigating N2O emissions is not easy. To derive national coefficients for N2O emissions from soil, we collated over 400 treatment evaluations (measurements) of N2O fluxes from farming systems in various ecoregions across Canada. A simple linear coefficient for fertilizer-induced emission
of N2O in non-manured soils (1.18% of N applied) was comparable to that used by the Intergovernmental Panel on Climate Change (IPCC)
(1.25% of N applied). Emissions were correlated to soil and crop management practices (manure addition, N fertilizer addition
and inclusion of legumes in the rotation) as well as to annual precipitation. The effect of tillage on emissions was inconsistent,
varying among experiments and even within experiments from year to year. In humid regions (e.g., Eastern Canada) no-tillage
tended to enhance N2O emissions; in arid regions (e.g., Western Prairies) no-tillage sometimes reduced emissions. The variability of N2O fluxes shows that we cannot yet always distinguish between potential mitigation practices with small (e.g., <10%) differences
in emission. Our analysis also emphasizes the need for developing consistent experimental approaches (e.g., ‘control’ treatments)
and methodologies (i.e. measurement period lengths) for estimating N2O emissions. 相似文献
11.
Effects of matrix moisture on gas diffusion and flow in coal 总被引:1,自引:0,他引:1
Gas production from coal is a complex process whereby gas, initially adsorbed in the coal matrix, desorbs and diffuses through the matrix into the cleat and eventually flows through the cleat system into a production well or a drainage borehole. Hence, the gas production rate is mainly controlled by the gas diffusivity in the matrix and gas permeability in the cleat system. Moisture in the coal matrix has significant impact on gas adsorption capacity and would also play a key role in desorption and migration of gas. However, how moisture affects gas desorption and diffusion in the coal matrix is still poorly understood. In this work, experimental study is performed to investigate effects of moisture on gas sorption rate for an Australian coal. Coal seam gases, CH4 and CO2, are used in the study. The experimental results show that moisture content in the matrix has significant impact on the gas sorption rate and the impact of moisture content on the diffusion rate is stronger for CH4 than CO2. Moreover, the impact of moisture on gas diffusivity in pores with different size is different, suggested from the modelling results using the bidisperse approach. Furthermore, moisture in coal matrix would cause coal swelling/shrinkage and mechanical properties change that could impact on coal permeability under reservoir conditions. Experimental measurements of coal matrix swelling and Young’s modulus on the same coal sample show that matrix moisture content has significant impact on those properties and may have significant implications on coalbed methane recovery and CO2 storage in coal. 相似文献
12.
Shujuan Wang Fang Liu Changhe Chen Xuchang Xu 《Korean Journal of Chemical Engineering》2007,24(3):495-498
It is thought that the CO2 emissions from coal-fired power plants contribute greatly to the total anthropogenic CO2 emissions. Ammonia solvent can be used to absorb the CO2, called ammonia scrubbing. However, as has been pointed out, the production of ammonia would emit CO2; therefore, the effectiveness of ammonia scrubbing is doubted. The paper focuses on the problem. Two systems are defined
in the paper. System I is CO2 absorption by ammonia scrubbing, and system II is industrial production of ammonium bicarbonate. The total CO2 emissions of the two systems are calculated by means of life cycle assessment. The paper shows that the total CO2 emissions of ammonia scrubbing are less than that of the industrial production of fertilizer ammonium bicarbonate. It can
be concluded that ammonia scrubbing is an effective way to reduce the anthropogenic CO2 emissions.
This work was presented at the 6
th
Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006. 相似文献
13.
This paper describes a series of experiments conducted with natural gas in air and in mixtures of oxygen and recycled flue gas, termed O2/CO2 recycle combustion. The objective is to enrich the flue gas with CO2 to facilitate its capture and sequestration. Detailed measurements of gas composition, flame temperature and heat flux profiles were taken inside CANMET's 0.3 MWth down-fired vertical combustor fitted with a proprietary pilot scale burner. Flue gas composition was continuously monitored. The effects of burner operation, including swirling of secondary stream and air staging, on flame characteristics and NOx emissions were also studied. The results of this work indicate that oxy-gas combustion techniques based on O2/CO2 combustion with flue gas recycle offer excellent potential for retrofit to conventional boilers for CO2 emission abatement. Other benefits of the technology include considerable reduction and even elimination of NOx emissions, improved plant efficiency due to lower gas volume and better operational flexibility. 相似文献
14.
G.X.WANG X.R.WEI V.RUDOLPH C.T.WEI Y.QIN 《Frontiers of Chemical Engineering in China》2009,3(1):20-25
This paper presents a multi-scale model to simulate the multicomponent gas diffusion and flow in bulk coals for CO2 sequestration enhanced coalbed methane recovery. The model is developed based on a bi-dispersed structure model by assuming
that coal consists of microporous micro-particles, meso/macro-pores and open microfractures. The bi-disperse diffusion theory
and the Maxwell-Stefan approach were incorporated in the model, providing an improved simulation of the CH4-CO2/CH4-N2 counter diffusion dynamics. In the model, the counter diffusion process is numerically coupled with the flow of the mixture
gases occurring within macro-pores or fractures in coal so as to account for the interaction between diffusion and flow in
gas transport through coals. The model was validated by both experimental data from literature and our CO2 flush tests, and shows an excellent agreement with the experiments. The results reveal that the gas diffusivities, in particular
the micro-pore diffusivities are strongly concentration-dependent. 相似文献
15.
Mid-day field fluxes of nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) were measured during late winter/early spring in an arable field and an adjacent fallow in southern Germany. On the arable field, 2 dm high ridges, drawn as seed-beds for potato, were exposed to mild, partly diurnal freezing–thawing. Substantially elevated N2O emission rates (6–750 µg N2O-N m–2 h–1) were observed throughout the investigation period which coincided with freezing–thawing events in the surface soil (0–5 cm). Soil temperatures in the densely vegetated fallow were more isothermal due to an insulating snow/ice cover, resulting in much lower N2O emission rates (0–57 µg N2O-N m–2 h–1). CH4 uptake rates were low in both habitats during soil frost (+2 to –7.5 µg CH4-C m–2 h–1) but increased markedly in the fallow after spring thaw. Our data suggest that N2O emission peaks may occur recurrently throughout the winter when soils are subjected to diurnal surface thawing. We concluded that microclimatic conditions strongly control N2O winter loss, thus overriding ecosystem-level differences in off-season nutrient cycling. To further characterize winter-time nutrient cycling and habitat functioning in our sites, we determined NO3
– and NH4
+ contents, fumigation-extractable carbon (Cmic) and nitrogen (Nmic) and enumerated protozoa and nematoda throughout the investigation period. Cmic and microbial C:N ratios in the fallow were higher in winter than during the rest of the year as indicated by a 2-year study, reflecting favorable conditions for microbial C assimilation at low temperatures in the absence of freeze–thaw perturbation. In the arable soil, Cmic contents were significantly reduced during soil freezing but recovered quickly upon warming of the soil. Dynamics of Cmic in the arable soil were paralleled by protozoan biomass and transient shifts in functional composition of the nematode community, indicating that microfaunal predation played an important role in nutrient cycling after freeze–thaw perturbation. Only minor microfaunal dynamics were observed in the climatically more stable fallow, essentially confirming the absence of perturbation at this site. Our findings provide strong evidence that overwinter N2O formation is regulated by both the physical freeze–thaw susceptibility of the soil and the ecological functioning of the habitat. 相似文献
16.
Miguel A. Bañares José H. Cardoso Graham J. Hutchings Jose M. Correa Bueno Jose L.G. Fierro 《Catalysis Letters》1998,56(2-3):149-153
The role of nitric oxide incorporation into the reaction feed for the partial oxidation of methane to C2-hydrocarbons and C2-oxygenates is evaluated. The addition of NO increases the conversion of methane under all the experimental conditions studied and has a strong effect on the product distribution. At low NO concentration the catalysts yield mainly C2Hn hydrocarbons, but at higher NO concentrations, carbon oxides dominate. Amongst the C1-oxygenates produced, methanol is the major compound observed and its proportion increases with increasing NO concentration. The highest C1-oxygenates yield was 7% at atmospheric pressure. This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
《分离科学与技术》2012,47(10):1385-1394
Carbon dioxide capture and storage (CCS) has been propounded as an important issue in greenhouse gas emissions control. In this connection, in the present article, the advantages of using polymeric membrane for separation of carbon dioxide from CO2/N2 streams have been discussed. A novel composition for fabrication of a blend membrane prepared from acrylonitrile-butadiene-styrene (ABS) terpolymer and polyethylene glycol (PEG) has been suggested. The influence of PEG molecular weight (in the range of 400 to 20000) on membrane characteristics and gas separation performance, the effect of PEG content (0–30 wt%) on gas transport properties, and the effect of feed side pressure (ranging from 1 to 8 bar) on CO2 permeability have been studied. The results show that CO2 permeability increases from 5.22 Barrer for neat ABS to 9.76 Barrer for ABS/PEG20000 (10 wt%) while the corresponding CO2/N2 selectivity increases from 25.97 to 44.36. Furthermore, it is concluded that this novel membrane composition has the potential to be considered as a commercial membrane. 相似文献
18.
Jianfeng Tang Dalong Zeng Chuanlei Wang Yuliang Chen Limin He Na Cai 《Chemical Engineering Research and Design》2013
Hydrate additives can be used to mitigate hydrate formation conditions, promote hydrate growth rate and improve separation efficiency. CO2 + N2 and CO2 + CH4 systems with presence of sodium dodecyl sulfate (SDS) or tetrahydrofuran (THF) are studied to analyze the effect of hydrate additives on gas separation performance. The experiment results show that CO2 can be selectively enriched in the hydrate phase. SDS can speed up the hydrate growth rate by facilitating gas molecules solubilization. When SDS concentration increases, split and loss fraction increase initially and then decrease slightly, resulting in a decreased separation factor. The optimum concentration of SDS exists at the range of 100–300 ppm. As THF can be easily encaged in hydrate cavities, hydrate formation condition can be mitigated greatly with its existence. Additionally, THF can also strengthen hydrate formation. The THF effect on separation performance is related to feed gas components. CO2 occupies the small cavities of type II hydrate prior to N2. But the competitiveness of CO2 and CH4 to occupy cavities are quite fair. The variations of split fraction, loss fraction and separation factor depend on the concentration of THF added. The work in this paper has a positive role in flue gas CO2 capture and natural gas de-acidification. 相似文献
19.
A series of A‐modified hexaaluminates, ANiAl11O19-δ (A = Ca, Sr, Ba and La) as new catalysts for carbon dioxide reforming of methane to synthesis gas, were prepared by decomposition
of nitrates and calcination at high temperature. Nickel ions as active component were inlayed in the hexaaluminate lattices
to substitute part of Al ions. The structure and properties of these samples were characterized using XRD, XPS, TPR and TGA
techniques. The series of hexaaluminates exhibited significantly catalytic activity and stability at high temperature, for
instance at 780°C for 18 h, the conversion of CH4 and CO2 was kept over 91.0 and 93.7%, respectively, meanwhile no Ni sintering, phase transformation and catalyst deactivation due
to carbon deposition were found. Besides, the modifier A in the mirror plane layer of the lattices showed different effects
on reducibility and catalytic activity of transition metal Ni in the hexaaluminate lattices.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
Experimental work has been carried out on the mixed reforming reaction, i.e., simultaneous steam and CO2 reforming of methane under a wide range of feed compositions and four different reaction temperatures from 700 °C to 850 °C using a commercial steam reforming catalyst. The experiments were conducted for a CO2/CH4 ratio from 0 to 2 and a steam to methane ratio from 3 to 5. The effect of CO2/CH4 ratio on the exit H2/CO ratio and the conversions of the reactants indicate that the dry reforming reaction is dominant under increased carbon dioxide in the feed. Steam reforming of typical steam hydrogasification product gas consisting of CO, H2 and CO2 in addition to steam and methane has also been investigated. The H2/CO ratio of the product synthesis gas varies from 4.3 to 3.7 and from 4.8 to 4.1 depending on the feed composition and reaction temperature. The CO/CO2 ratios of the synthesis gas varied from 1.9 to 2.9 and 2.0 to 3.3. The results are compared with simulation results obtained through the Aspen Plus process simulation tool. The results demonstrate that a coupled steam hydrogasification and reforming process can generate a synthesis gas with a flexible H2/CO ratio from carbon-containing feedstocks. 相似文献