Biogas upgrading for removing CO2 and other trace components from raw biogas is a necessary step before the biogas to be used as a vehicle fuel or supplied to the natural gas grid. In this work, three technologies for...Biogas upgrading for removing CO2 and other trace components from raw biogas is a necessary step before the biogas to be used as a vehicle fuel or supplied to the natural gas grid. In this work, three technologies for biogas upgrading, i.e., pressured water scrubbing(PWS), monoethanolamine aqueous scrubbing(MAS) and ionic liquid scrubbing(ILS), are studied and assessed in terms of their energy consumption and environmental impacts with the process simulation and green degree method. A non-random-two-liquid and Henry's law property method for a CO2 separation system with ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([bmim][Tf2N]) is established and verified with experimental data. The assessment results indicate that the specific energy consumption of ILS and PWS is almost the same and much less than that of MAS. High purity CO2 product can be obtained by MAS and ILS methods, whereas no pure CO2 is recovered with the PWS. For the environmental aspect, ILS has the highest green degree production value, while MAS and PWS produce serious environmental impacts.展开更多
Significant attention has been given to biogas production, purification and upgrading as a renewable and clean fuel supplement. Biogas is a product of an anaerobic digestion process comprising methane, carbon dioxide,...Significant attention has been given to biogas production, purification and upgrading as a renewable and clean fuel supplement. Biogas is a product of an anaerobic digestion process comprising methane, carbon dioxide,and trace amounts of other gases. Biogas purification removes trace gases in biogas for safe utilisation. Biogas upgrading produces methane-rich biogas by removing bulk carbon dioxide from the gas mixture. Several carbon dioxide removal techniques can be applied for biogas upgrading. However, chemical absorption of carbon dioxide for biogas upgrading is of special significance due to its operation at ambient or near ambient temperature and pressure, thus reducing energy consumption. This paper reviews the chemical absorption of carbon dioxide using amine scrubbing, caustic solvent scrubbing, and amino acid salt solution scrubbing. Each of these techniques for biogas upgrading is discussed. The paper concludes that an optimised implementation of the chemical absorption techniques for biogas upgrading requires further research.展开更多
Rotating bed can be used in desorption operation of biogas upgrading as a new technology. For enough time to desorb, it is important to study the relationship between the residence time of liquid in rotating bed and t...Rotating bed can be used in desorption operation of biogas upgrading as a new technology. For enough time to desorb, it is important to study the relationship between the residence time of liquid in rotating bed and the material diffusion time of liquid droplet in desorption process. By theoretical deduction, the exponential relation between residence time and liquid flow rate and rotational speed and kinematic viscosity is obtained. By analyzing the solution of nonlinear partial differential equation, the time law of material diffusion in the droplet is obtained. Moreover, by comparing the residence and diffusion times, the diffusion time can be within or out of residence time range, which has a direct relationship to rotational speed and liquid flow. By experiment, the comparison between residence and diffusion times is more realistic when the rotational speed is higher.展开更多
A shift to renewable energy sources will reduce emissions of greenhouse gases and secure future energy supplies. In this context, utilization of biogas will play a prominent role. Focus of this work is upgrading of bi...A shift to renewable energy sources will reduce emissions of greenhouse gases and secure future energy supplies. In this context, utilization of biogas will play a prominent role. Focus of this work is upgrading of biogas to fuel quality by membrane separation using a carbon hollow fibre(CHF) membrane and compare with a commercially available polymeric membrane(polyimide) through economical assessment. CHF membrane modules were prepared for pilot plant testing and performance measured using CO_2, O_2, N_2. The CHF membrane was modified through oxidation, chemical vapour deposition(CVD) and reduction process thus tailoring pores for separation and increased performance. The post oxidized and reduced carbon hollow fibres(PORCHFs) significantly exceeded CHF performance showing higher CO_2 permeance(0.021 m^3(STP)/m^2 h bar) and CO_2/CH_4 selectivity of 246(5 bar feed vs 50 mbar permeate pressure). The highest performance recorded through experiments(CHF and PORCHF) was used as simulation basis. A membrane simulation model was used and interfaced to 8.6 V Aspen HYSYS.A 300 Nm^3/h mixture of CO_2/CH_4 containing 30-50% CO_2 at feed pressures 6, 8 and 10 bar, was simulated and process designed to recover99.5% CH_4 with 97.5% purity. Net present value(NPV) was calculated for base case and optimal pressure(50 bar for CHF and PORCHF). The results indicated that recycle ratio(recycle/feed) ranged from 0.2 to 10, specific energy from 0.15 to 0.8(kW/Nm^3 feed) and specific membrane area from 45 to 4700(m^2/Nm^3 feed). The high recycle ratio can create problems during start-up, as it would take long to adjust volumetric flow ratio towards 10. The best membrane separation system employs a three-stage system with polyimide at 10 bar, and a two-stage membrane system with PORCHF membranes at 50 bar with recycle. Considering biomethane price of 0.78 $/Nm^3 and a lifetime of 15 years, the technoeconomic analysis showed that payback time for the best cascade is 1.6 months.展开更多
This study focused on enhancing the efficiency of methane upgrading and reducing energy consumption in the biogas upgrading process through the use of biphasic solvents.An aqueous-based biphasic solvent,comprising met...This study focused on enhancing the efficiency of methane upgrading and reducing energy consumption in the biogas upgrading process through the use of biphasic solvents.An aqueous-based biphasic solvent,comprising methyl monoethanolamine(MMEA),N-methyldiethanolamine(MDEA),and 1-butyl-3-methylimidazolium tetrafluoroborate(ItFB),was meticulously prepared.The biogas upgrading effect,regeneration efficiency,regeneration energy consumption,economic viability,selectivity,and phase separation characteristics of this absorbent were systematically analyzed.Various parameters,including different inlet flow rates,stirring rate,methane inlet concentrations,reaction temperatures,and amine mixing ratios,were adjusted to investigate their impact.A comprehensive evaluation was conducted on the biogas upgrading effect and substance migration trends of the biphasic solvent.Optimal process parameters were determined,demonstrating the favorable impact of the biphasic solvent on biogas upgrading.The upgraded gas achieved a methane purity exceeding 96%,and the regeneration energy consumption decreased by 44.27% compared to 30 wt.%MEA,resulting in a more than 50% improvement in economic efficiency.The interaction between the ionic liquid and carbamate facilitated the phase separation process,with carbon enrichment after separation exceeding 95%.This enhancement significantly contributed to the improvement of regeneration energy consumption.The study thus concludes that biphasic solvents,exemplified by the described aqueous-based solution,offer a promising avenue for effective biogas upgrading with notable advancements in economic and energy efficiency.展开更多
The energy contents of biogas could be significantly enhanced by upgrading it to vehicle fuel quality.A pilot-scale separation plant based on carbon hollow fiber membranes for upgrading biogas to vehicle fuel quality ...The energy contents of biogas could be significantly enhanced by upgrading it to vehicle fuel quality.A pilot-scale separation plant based on carbon hollow fiber membranes for upgrading biogas to vehicle fuel quality was constructed and operated at the biogas plant,Gl?r IKS,Lillehammer Norway.Vehicle fuel quality according to Swedish legislation was successfully achieved in a single stage separation process.The raw biogas from anaerobic digestion of food waste contained 64±3 mol%CH_4,30–35 mol%CO_2 and less than one percent of N_2 and a minor amount of other impurities.The raw biogas was available at 1.03 bar with a maximum flow rate of 60 Nm^3h^(à1).Pre-treatment of biogas was performed to remove bulk H_2O and H_2S contents up to the required limits in the vehicle fuel before entering to membrane system.The membrane separation plant was designed to process 60 Nm^3h^(à1)of raw biogas at pressure up to 21 bar.The initial tests were,however,performed for the feed flow rate of 10 Nm^3h^(à1)at 21 bar.The successful operation of the pilot plant separation was continuously run for 192 h(8days).The CH_4 purity of 96%and maximum CH_4 recovery of 98%was reached in a short-term test of 5 h.The permeate stream contained over20 mol%CH_4which could be used for the heating application.Aspen Hysys~?was integrated with Chem Brane(in-house developed membrane model)to run the simulations for estimation of membrane area and energy requirement of the pilot plant.Cost estimation was performed based on simulation data and later compared with actual field results.展开更多
Biogas is a renewable source of energy that when upgraded can be adopted as a reliable and sustainable alternative.This study evaluates the performance of thermal swing adsorption technology applying resistive heating...Biogas is a renewable source of energy that when upgraded can be adopted as a reliable and sustainable alternative.This study evaluates the performance of thermal swing adsorption technology applying resistive heating,in upgrading biogas obtained from anaerobic digestion to biomethane.Commercial coconut shell-based activated carbon was used as an adsorbent in the four-step cycle process to capture carbon dioxide,using a fabricated adsorption model.The influence of minor gas constituents of biogas in carbon dioxide breakthrough curves was analyzed.Dynamic adsorption tests were carried out to evaluate the system performance in carbon dioxide capture.The maximum regeneration temperature of 60℃was found to have peak carbon dioxide concentration of 39%in the waste gas,maximum energy requirements of 0.1538 kWh per cycle,and an energy efficiency of 87%.This is a good trade-off between adsorbent recovery and system energy efficiency.The adoption of thermal swing adsorption technology in biogas upgrading systems is a viable alternative for water-deficient regions.展开更多
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
Membrane separation technology offers a green,efficient and energy-saving approach for biogas upgrading.Membranes with high selectivity and high permeability are the key to achieve high performance.Polymers of Intrins...Membrane separation technology offers a green,efficient and energy-saving approach for biogas upgrading.Membranes with high selectivity and high permeability are the key to achieve high performance.Polymers of Intrinsic Microporosity(PIMs)materials have shown excellent gas permeability but low selectivity which limits their practical application.Herein,a polyphenol,tannic acid,was coated on the PIM-1 membrane surface by a facile dipping method to fabricate composite membranes.Tannic acid containing a large number of polar oxygencontaining groups(quinone,phenolic hydroxyl)self-polymerized on the membrane surface to form a CO2-philic,defect-free and thin layer.The CO2/CH4 selectivity of the resultant composite membranes was increased after tannic acid coating while the permeability remained comparable to or even higher than pristine PIM-1 membrane,exceeding the reported 2008 upper bound.展开更多
基金Supported by the National Basic Research Program of China(2013CB733506,2014CB744306)the National Natural Science Foundation of China(21036007,51274183)
文摘Biogas upgrading for removing CO2 and other trace components from raw biogas is a necessary step before the biogas to be used as a vehicle fuel or supplied to the natural gas grid. In this work, three technologies for biogas upgrading, i.e., pressured water scrubbing(PWS), monoethanolamine aqueous scrubbing(MAS) and ionic liquid scrubbing(ILS), are studied and assessed in terms of their energy consumption and environmental impacts with the process simulation and green degree method. A non-random-two-liquid and Henry's law property method for a CO2 separation system with ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([bmim][Tf2N]) is established and verified with experimental data. The assessment results indicate that the specific energy consumption of ILS and PWS is almost the same and much less than that of MAS. High purity CO2 product can be obtained by MAS and ILS methods, whereas no pure CO2 is recovered with the PWS. For the environmental aspect, ILS has the highest green degree production value, while MAS and PWS produce serious environmental impacts.
文摘Significant attention has been given to biogas production, purification and upgrading as a renewable and clean fuel supplement. Biogas is a product of an anaerobic digestion process comprising methane, carbon dioxide,and trace amounts of other gases. Biogas purification removes trace gases in biogas for safe utilisation. Biogas upgrading produces methane-rich biogas by removing bulk carbon dioxide from the gas mixture. Several carbon dioxide removal techniques can be applied for biogas upgrading. However, chemical absorption of carbon dioxide for biogas upgrading is of special significance due to its operation at ambient or near ambient temperature and pressure, thus reducing energy consumption. This paper reviews the chemical absorption of carbon dioxide using amine scrubbing, caustic solvent scrubbing, and amino acid salt solution scrubbing. Each of these techniques for biogas upgrading is discussed. The paper concludes that an optimised implementation of the chemical absorption techniques for biogas upgrading requires further research.
基金Supported by the Special Scientific Research Fund of Agricultural Public Welfare Profession of China(201303099)
文摘Rotating bed can be used in desorption operation of biogas upgrading as a new technology. For enough time to desorb, it is important to study the relationship between the residence time of liquid in rotating bed and the material diffusion time of liquid droplet in desorption process. By theoretical deduction, the exponential relation between residence time and liquid flow rate and rotational speed and kinematic viscosity is obtained. By analyzing the solution of nonlinear partial differential equation, the time law of material diffusion in the droplet is obtained. Moreover, by comparing the residence and diffusion times, the diffusion time can be within or out of residence time range, which has a direct relationship to rotational speed and liquid flow. By experiment, the comparison between residence and diffusion times is more realistic when the rotational speed is higher.
文摘A shift to renewable energy sources will reduce emissions of greenhouse gases and secure future energy supplies. In this context, utilization of biogas will play a prominent role. Focus of this work is upgrading of biogas to fuel quality by membrane separation using a carbon hollow fibre(CHF) membrane and compare with a commercially available polymeric membrane(polyimide) through economical assessment. CHF membrane modules were prepared for pilot plant testing and performance measured using CO_2, O_2, N_2. The CHF membrane was modified through oxidation, chemical vapour deposition(CVD) and reduction process thus tailoring pores for separation and increased performance. The post oxidized and reduced carbon hollow fibres(PORCHFs) significantly exceeded CHF performance showing higher CO_2 permeance(0.021 m^3(STP)/m^2 h bar) and CO_2/CH_4 selectivity of 246(5 bar feed vs 50 mbar permeate pressure). The highest performance recorded through experiments(CHF and PORCHF) was used as simulation basis. A membrane simulation model was used and interfaced to 8.6 V Aspen HYSYS.A 300 Nm^3/h mixture of CO_2/CH_4 containing 30-50% CO_2 at feed pressures 6, 8 and 10 bar, was simulated and process designed to recover99.5% CH_4 with 97.5% purity. Net present value(NPV) was calculated for base case and optimal pressure(50 bar for CHF and PORCHF). The results indicated that recycle ratio(recycle/feed) ranged from 0.2 to 10, specific energy from 0.15 to 0.8(kW/Nm^3 feed) and specific membrane area from 45 to 4700(m^2/Nm^3 feed). The high recycle ratio can create problems during start-up, as it would take long to adjust volumetric flow ratio towards 10. The best membrane separation system employs a three-stage system with polyimide at 10 bar, and a two-stage membrane system with PORCHF membranes at 50 bar with recycle. Considering biomethane price of 0.78 $/Nm^3 and a lifetime of 15 years, the technoeconomic analysis showed that payback time for the best cascade is 1.6 months.
基金the financial support by the National Natural Science Foundation of China(No.22376115)funded by the Shanghai Tongji Gao Tingyao Environmental Science&Technology Development Foundation(China).
文摘This study focused on enhancing the efficiency of methane upgrading and reducing energy consumption in the biogas upgrading process through the use of biphasic solvents.An aqueous-based biphasic solvent,comprising methyl monoethanolamine(MMEA),N-methyldiethanolamine(MDEA),and 1-butyl-3-methylimidazolium tetrafluoroborate(ItFB),was meticulously prepared.The biogas upgrading effect,regeneration efficiency,regeneration energy consumption,economic viability,selectivity,and phase separation characteristics of this absorbent were systematically analyzed.Various parameters,including different inlet flow rates,stirring rate,methane inlet concentrations,reaction temperatures,and amine mixing ratios,were adjusted to investigate their impact.A comprehensive evaluation was conducted on the biogas upgrading effect and substance migration trends of the biphasic solvent.Optimal process parameters were determined,demonstrating the favorable impact of the biphasic solvent on biogas upgrading.The upgraded gas achieved a methane purity exceeding 96%,and the regeneration energy consumption decreased by 44.27% compared to 30 wt.%MEA,resulting in a more than 50% improvement in economic efficiency.The interaction between the ionic liquid and carbamate facilitated the phase separation process,with carbon enrichment after separation exceeding 95%.This enhancement significantly contributed to the improvement of regeneration energy consumption.The study thus concludes that biphasic solvents,exemplified by the described aqueous-based solution,offer a promising avenue for effective biogas upgrading with notable advancements in economic and energy efficiency.
文摘The energy contents of biogas could be significantly enhanced by upgrading it to vehicle fuel quality.A pilot-scale separation plant based on carbon hollow fiber membranes for upgrading biogas to vehicle fuel quality was constructed and operated at the biogas plant,Gl?r IKS,Lillehammer Norway.Vehicle fuel quality according to Swedish legislation was successfully achieved in a single stage separation process.The raw biogas from anaerobic digestion of food waste contained 64±3 mol%CH_4,30–35 mol%CO_2 and less than one percent of N_2 and a minor amount of other impurities.The raw biogas was available at 1.03 bar with a maximum flow rate of 60 Nm^3h^(à1).Pre-treatment of biogas was performed to remove bulk H_2O and H_2S contents up to the required limits in the vehicle fuel before entering to membrane system.The membrane separation plant was designed to process 60 Nm^3h^(à1)of raw biogas at pressure up to 21 bar.The initial tests were,however,performed for the feed flow rate of 10 Nm^3h^(à1)at 21 bar.The successful operation of the pilot plant separation was continuously run for 192 h(8days).The CH_4 purity of 96%and maximum CH_4 recovery of 98%was reached in a short-term test of 5 h.The permeate stream contained over20 mol%CH_4which could be used for the heating application.Aspen Hysys~?was integrated with Chem Brane(in-house developed membrane model)to run the simulations for estimation of membrane area and energy requirement of the pilot plant.Cost estimation was performed based on simulation data and later compared with actual field results.
基金supported in part by the German Academic Exchange Service(DAAD)and Japan International Cooperation Agency(JICA)through the AFRICA-ai-JAPAN project(Grant No.:iPIC/C2/07/22).
文摘Biogas is a renewable source of energy that when upgraded can be adopted as a reliable and sustainable alternative.This study evaluates the performance of thermal swing adsorption technology applying resistive heating,in upgrading biogas obtained from anaerobic digestion to biomethane.Commercial coconut shell-based activated carbon was used as an adsorbent in the four-step cycle process to capture carbon dioxide,using a fabricated adsorption model.The influence of minor gas constituents of biogas in carbon dioxide breakthrough curves was analyzed.Dynamic adsorption tests were carried out to evaluate the system performance in carbon dioxide capture.The maximum regeneration temperature of 60℃was found to have peak carbon dioxide concentration of 39%in the waste gas,maximum energy requirements of 0.1538 kWh per cycle,and an energy efficiency of 87%.This is a good trade-off between adsorbent recovery and system energy efficiency.The adoption of thermal swing adsorption technology in biogas upgrading systems is a viable alternative for water-deficient regions.
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This work was supported by National Natural Science Foundation of China(No.U20B2023,21838008,21621004)Program of Introducing Talents of Discipline to Universities(No.BP0618007).
文摘Membrane separation technology offers a green,efficient and energy-saving approach for biogas upgrading.Membranes with high selectivity and high permeability are the key to achieve high performance.Polymers of Intrinsic Microporosity(PIMs)materials have shown excellent gas permeability but low selectivity which limits their practical application.Herein,a polyphenol,tannic acid,was coated on the PIM-1 membrane surface by a facile dipping method to fabricate composite membranes.Tannic acid containing a large number of polar oxygencontaining groups(quinone,phenolic hydroxyl)self-polymerized on the membrane surface to form a CO2-philic,defect-free and thin layer.The CO2/CH4 selectivity of the resultant composite membranes was increased after tannic acid coating while the permeability remained comparable to or even higher than pristine PIM-1 membrane,exceeding the reported 2008 upper bound.
