CO_(2) in natural gas(NG)is prone to condense directly from gas to solid or solidify from liquid to solid at low temperatures due to its high triple point and boiling temperature,which can cause a block of equipment.M...CO_(2) in natural gas(NG)is prone to condense directly from gas to solid or solidify from liquid to solid at low temperatures due to its high triple point and boiling temperature,which can cause a block of equipment.Meanwhile,CO_(2) will also affect the calorific value of NG.Based on the above reasons,CO_(2) must be removed during the NG liquefaction process.Compared with conventional methods,cryogenic technologies for CO_(2) removal from NG have attracted wide attention due to their nonpolluting and low-cost advantages.Its integration with NG liquefaction can make rational use of the cold energy and realize the purification of NG and the production of byproduct liquid CO_(2).In this paper,the phase behavior of the CH_(4)-CO_(2) binary mixture is summarized,which provides a basis for the process design of cryogenic CO_(2) removal from NG.Then,the detailed techniques of design and optimization for cryogenic CO_(2) removal in recent years are summarized,including the gas-liquid phase change technique and the gas-solid phase change technique.Finally,several improvements for further development of the cryogenic CO_(2) removal process are proposed.The removal process in combination with the phase change and the traditional techniques with renewable energy will be the broad prospect for future development.展开更多
A kind of new catalyst-carbonaceous catalyst-for CH_(4)-CO_(2) reformation has been developed in our laboratory.The effect of both oxygen-bearing functional group such as phenolic hydroxyl,carbonyl,carboxyl,and lacton...A kind of new catalyst-carbonaceous catalyst-for CH_(4)-CO_(2) reformation has been developed in our laboratory.The effect of both oxygen-bearing functional group such as phenolic hydroxyl,carbonyl,carboxyl,and lactonic,and ash such as Fe_(2)O_(3),Na_(2)CO_(3),and K_(2)CO_(3) in the carbonaceous catalyst on the CH_(4)-CO_(2) reforming has been investigated with a fixed-bed reactor.It has been found that the carbonaceous catalyst is an efficient catalyst on CO_(2)-CH_(4) reforming.With the decrease of oxygen-bearing functional group,the catalytic activity of carbonaceous catalyst decreases quickly.The oxygen-bearing functional groups play a significant role in the carbonaceous-catalyzed CO_(2)-CH_(4) reforming;the ash components in carbonaceous catalyst also have an important influence on the CO_(2)-CH_(4) reforming.Fe_(2)O_(3),Na_(2)CO_(3),and K_(2)CO_(3) in the ash can catalyze the CO_(2)-CH_(4) reforming reaction;CaO has little effect on CO_(2)-CH_(4) reforming reaction.CaO can catalyze the gasification between carbonaceous catalyst and CO_(2);Al_(2)O_(3) and MgO inhibit the CO_(2)-CH_(4) reforming.展开更多
An investigation was made using a continuous fixed bed reactor to understand the influence of carbon deposition obtained under different conditions on CH_(4)-CO_(2)reforming.Thermogravimetry(TG)and X-ray diffraction(X...An investigation was made using a continuous fixed bed reactor to understand the influence of carbon deposition obtained under different conditions on CH_(4)-CO_(2)reforming.Thermogravimetry(TG)and X-ray diffraction(XRD)were employed to study the characteristics of carbon deposition.It was found that the carbonaceous catalyst is an efficient catalyst in methane decomposition and CH_(4)-CO_(2)reforming.The trend of methane decomposition at lower temperatures is similar to that at higher temperatures.The methane conversion is high during the initial of stage of the reaction,and then decays to a relatively fixed value after about 30 min.With temperature increase,the methane decomposition rate increases quickly.The reaction temperature has significant influence on methane decomposition,whereas the carbon deposition does not affect methane decomposition significantly.Different types of carbon deposition were formed at different methane decomposition reaction temperatures.The carbon deposition Type I generated at 900℃ has a minor effect on CH_(4)-CO_(2)reforming and it easily reacts with carbon dioxide,but the carbon deposition Type II generated at 1000℃and 1100℃clearly inhibits CH_(4)-CO_(2)reforming and it is difficult to react with carbon dioxide.The results of XRD showed that some graphite structures were found in carbon deposition Type II.展开更多
文摘CO_(2) in natural gas(NG)is prone to condense directly from gas to solid or solidify from liquid to solid at low temperatures due to its high triple point and boiling temperature,which can cause a block of equipment.Meanwhile,CO_(2) will also affect the calorific value of NG.Based on the above reasons,CO_(2) must be removed during the NG liquefaction process.Compared with conventional methods,cryogenic technologies for CO_(2) removal from NG have attracted wide attention due to their nonpolluting and low-cost advantages.Its integration with NG liquefaction can make rational use of the cold energy and realize the purification of NG and the production of byproduct liquid CO_(2).In this paper,the phase behavior of the CH_(4)-CO_(2) binary mixture is summarized,which provides a basis for the process design of cryogenic CO_(2) removal from NG.Then,the detailed techniques of design and optimization for cryogenic CO_(2) removal in recent years are summarized,including the gas-liquid phase change technique and the gas-solid phase change technique.Finally,several improvements for further development of the cryogenic CO_(2) removal process are proposed.The removal process in combination with the phase change and the traditional techniques with renewable energy will be the broad prospect for future development.
基金the National Basic Research Program of China(2005CB221202)Shanxi Provincial Natural Science Foundation(20051020)for financial support of the present study。
文摘A kind of new catalyst-carbonaceous catalyst-for CH_(4)-CO_(2) reformation has been developed in our laboratory.The effect of both oxygen-bearing functional group such as phenolic hydroxyl,carbonyl,carboxyl,and lactonic,and ash such as Fe_(2)O_(3),Na_(2)CO_(3),and K_(2)CO_(3) in the carbonaceous catalyst on the CH_(4)-CO_(2) reforming has been investigated with a fixed-bed reactor.It has been found that the carbonaceous catalyst is an efficient catalyst on CO_(2)-CH_(4) reforming.With the decrease of oxygen-bearing functional group,the catalytic activity of carbonaceous catalyst decreases quickly.The oxygen-bearing functional groups play a significant role in the carbonaceous-catalyzed CO_(2)-CH_(4) reforming;the ash components in carbonaceous catalyst also have an important influence on the CO_(2)-CH_(4) reforming.Fe_(2)O_(3),Na_(2)CO_(3),and K_(2)CO_(3) in the ash can catalyze the CO_(2)-CH_(4) reforming reaction;CaO has little effect on CO_(2)-CH_(4) reforming reaction.CaO can catalyze the gasification between carbonaceous catalyst and CO_(2);Al_(2)O_(3) and MgO inhibit the CO_(2)-CH_(4) reforming.
基金the National Basic Research Program of China(Grant No.2005CB221202)Shanxi Provincial Natural Science Foundation(20051020)for financial support of the present study。
文摘An investigation was made using a continuous fixed bed reactor to understand the influence of carbon deposition obtained under different conditions on CH_(4)-CO_(2)reforming.Thermogravimetry(TG)and X-ray diffraction(XRD)were employed to study the characteristics of carbon deposition.It was found that the carbonaceous catalyst is an efficient catalyst in methane decomposition and CH_(4)-CO_(2)reforming.The trend of methane decomposition at lower temperatures is similar to that at higher temperatures.The methane conversion is high during the initial of stage of the reaction,and then decays to a relatively fixed value after about 30 min.With temperature increase,the methane decomposition rate increases quickly.The reaction temperature has significant influence on methane decomposition,whereas the carbon deposition does not affect methane decomposition significantly.Different types of carbon deposition were formed at different methane decomposition reaction temperatures.The carbon deposition Type I generated at 900℃ has a minor effect on CH_(4)-CO_(2)reforming and it easily reacts with carbon dioxide,but the carbon deposition Type II generated at 1000℃and 1100℃clearly inhibits CH_(4)-CO_(2)reforming and it is difficult to react with carbon dioxide.The results of XRD showed that some graphite structures were found in carbon deposition Type II.
