变压吸附在沼气脱碳中的应用

采用变压吸附法(PSA)对沼气中CH4-CO2混合物进行分离研究。在四塔变压吸附装置上进行中试试验,对相同环境温度和不同环境温度两种工况下不同原料气组成,分别测定了变压吸附脱碳前后气体中CH4和CO2的体积含量,沼气经变压吸附法脱碳后,净化气中CH4浓度高达97%以上,CO2含量低于1%,CH4回收率为94%。试验证明,变压吸附脱碳技术成本小、能耗低、运行基本不受环境温度影响,在沼气脱碳中具有良好的应用前景。     

加压水洗沼气脱碳的实验研究

利用加压水洗提纯沼气小试实验装置,研究了进水流量、进气流量、吸收压力和吸收温度对沼气加压水洗脱碳过程中CO2去除率、CH4回收率和CO2饱和度等参数的影响。结果表明:增大吸收压力和降低吸收温度可显著提升加压水洗脱碳效果,增大进水流量和减小进气流量可以提高CO2去除率和产品气的纯度;CO2去除率越高,CH4回收率和产气率越低;当进水流量为100 m L/min、进气流量为800 m L/min、吸收温度为10℃、吸收压力为0.8~1.0 MPa时,产品气中的CO2含量可控制在3%以下,能够满足车用压缩天然气技术标准的要求。     

填料塔中碳酸丙烯酯脱除沼气中的CO_2

以木薯渣发酵产生的沼气为原料气,采用10 m3/d脱碳工艺试验装置,以碳酸丙烯酯为吸收剂脱除沼气中的CO2,分别考察了吸收气液比、吸收压力、吸收温度、空气气提气液比、原料沼气中硫化氢浓度对脱碳效果的影响。试验结果表明,吸收气液比为55、吸收压力为800 kPa、吸收温度15℃、空气气提气液比为10时,净化气中CO2浓度为(6.44±0.34)%,CO2脱除率为(92.48±0.39)%。原料沼气中H2S浓度对碳酸丙烯酯的脱碳效果影响显著,当H2S浓度增加到0.4%时,与以脱硫后沼气为原料气时的脱碳情况相比,净化气中CO2浓度增加了1.66%。     

膜分离法、化学吸收法以及联合法分离CO_2/CH_4试验比较

在中空纤维膜和化学吸收塔的试验台上,分别采用膜分离法、化学吸收法进行了CO2/CH4混合气体的分离试验.在此基础上提出了联合法新型CO2脱除技术,并在中空纤维膜串联化学吸收塔的试验台上进行了CO2/CH4混合气体分离试验,重点考察了各影响因素对各分离方法脱碳效果的影响,并对各分离方法脱碳效果进行了对比.结果表明:膜分离法的脱碳效率低且CH4损失率高,适用于处理小流量且对脱碳效率要求不高的工艺;化学吸收法的脱碳效率和CH4回收率高,适用于分离纯度要求高的工艺;联合法脱碳效率偏低但CH4损失率低,适用于处理大流量且对脱碳效率要求不高的工艺.     

压力水洗法沼气脱碳的模拟研究

采用PRO II 8.0电解质模型模拟了压力水洗法沼气脱碳单元的运行成本和CH_4回收率,要求净化气CO_2浓度3.0%,CH_4收率96%。通过改变进口浓度、吸收塔理论板数、吸收压力、吸收温度、闪蒸压力和再生气-液比,模拟对运行成本和收率的影响。结果表明:高理论板数、低温、高压、高闪蒸压力有利于降低运行成本。吸收压力为0.8 MPa,吸收温度为5℃,闪蒸压力为0.35 MPa时,沼气压力水洗脱碳单元的运行成本为14.4分/m~3,CH_4回收率可以达到98.4%。     

La2O3改进Ni/γ-Al2O3催化剂上沼气重整制氢

为了寻求制备氢气的可再生资源及减少沼气的排放量,用浸渍法制备了不同La2O3含量的Ni/La2O3/γ Al2O3催化剂,用CH4/CO2体积比为1的混合气体模拟沼气,考察了还原温度、反应温度、空速等操作条件对该催化剂上沼气重整制氢性能的影响.并运用H2-TPR、TEM、TG-DSC等对催化剂进行了表征.结果表明:La2O3含量为6%的催化剂具有较好的综合性能;载体中掺杂适量La2O3能增加金属Ni的分散性,提高催化剂的可还原性及载体对CO2的吸附能力,从而改善了催化剂的活性及抗积炭性,使催化剂具有较好的稳定性.在100h的稳定性实验中,CH4及CO2转化率、H2及CO的选择性、H2/CO比平均值分别约为87.4%、88.8%、87.3%、93.8%及0.92.催化剂表面积炭速率非常低,仅为0.7279mg/(gcat·h).     

轿车柴油机燃用生物柴油时温室气体排放特性的研究

对轿车柴油机燃用大豆酸化油制生物柴油进行了试验研究,探讨了在外特性、标定转速负荷特性及最大扭矩转速负荷特性下尾气中CO2、CH4、N2O及当量CO2温室气体排放的变化规律.结果表明:轿车柴油机的CH4和N2O排放量均很小,CO2是其主要温室气体排放;随着生物柴油混合比例的增加,发动机的CO2和CH4排放降低,N2O升高,生命周期当量CO2排放降低.大豆酸化油制生物柴油能在一定程度上降低轿车柴油机的温室气体排放.     

两段式处理制取车用燃料级沼气的试验研究

以配制的模拟沼气为原料,采用水洗和可再生的碱金属基吸收剂干法吸收相结合的两段式处理流程来纯化沼气,以沸石颗粒作洗涤塔填料,附载Na2CO3的活性碳颗粒作干式吸收塔填料,制得的CH4含量在95%以上,达到车用燃料级的高纯沼气。     

Ni-Co双金属催化剂上沼气重整制氢宏观动力学

用传统湿式浸渍法制备La2O3掺杂的商业γ-Al2O3负载的沼气重整催化剂Ni-Co/La2O3-γ-Al2O3,通过对NiCo双金属催化剂上沼气重整制氢在常压下的宏观动力学分析,得出该催化剂上CH4与CO2消耗、H2与CO生成时的表观反应速率方程.通过改变进料中CH4与CO2的分压,求出各物质的反应分级数,确定总反应...     

生物沼气的应用与提纯

沼气作为一种洁净的能源,除用于传统的供热外,现在主要用于发电及作为车用压缩天然气或管道天然气.沼气的提纯主要包括脱硫、脱水、脱氧、脱碳等过程.变压吸附法脱碳与其他脱碳方法相比,无论从能耗还是工艺都具有很大优势,该方法用于沼气的脱碳具有广阔前景.     

Techno-economical evaluations of decarbonized hydrogen production based on direct biogas conversion using thermo-chemical looping cycles

Hydrogen production by biogas conversion represent a promising solution for reduction of fossil CO₂ emissions. In this work, a detailed techno-economic analysis was performed for decarbonized hydrogen production based on biogas conversion using calcium and chemical looping cycles. All evaluated concepts generate 100,000 Nm³/h high purity hydrogen. As reference cases, the biogas steam reforming design without decarbonization and with CO₂ capture by gas-liquid chemical absorption were also considered. The results show that iron-based chemical looping design has higher energy efficiency compared with the gas-liquid absorption case by 2.3 net percentage points as well as a superior carbon capture rate (99% vs. 65%). The calcium looping case shows a lower efficiency than chemical scrubbing, with about 2.5 net percentage points, but the carbon capture rate is higher (95% vs. 65%). The hydrogen production cost increases with decarbonization, the calcium looping shows the most favourable situation (37.14 €/MWh) compared to the non-capture steam reforming case (33 €/MWh) and MDEA and iron looping cases (about 42 €/MWh). The calcium looping case has the lowest CO₂ avoidance cost (10 €/t) followed by iron looping (20 €/t) and MDEA (31 €/t) cases.     

Biogas scrubbing, compression and storage: perspective and prospectus in Indian context

Biogas is a clean environment friendly fuel. Raw biogas contains about 55–65% methane (CH₄), 30–45% carbon dioxide (CO₂), traces of hydrogen sulfide (H₂S) and fractions of water vapours. Presently, it can be used only at the place where it is produced. There is a great need to make biogas transportable. This can be done by compressing the gas in cylinders which is possible only after removing its CO₂, H₂S and water vapour components. Pilot level trials to compress the biogas have been carried out by a number of earlier investigators working on the subject. This paper reviews the efforts made to improve the quality of biogas by scrubbing CO₂ and the results obtained. There is a lot of potential if biogas could be made viable as a transport vehicle fuel like CNG by compressing it and filling into cylinders after scrubbing and drying. Thus the need emerges for a unified approach for scrubbing, compressing and subsequent storage of biogas for wider applications.     

Performance evaluation of biogas upgrading systems from swine farm to biomethane production for renewable hydrogen source

Biogas upgrading to biomethane is a necessary process for biohydrogen production from renewable source. In this work, absorption processes using water and diethanolamine (DEA) as absorbent were modeled in Aspen Plus software. The purpose was to find the optimal operating condition for sustainable production of biomethane using multi-criteria perspective considering technical, environmental and economic aspects. The absorption system was modified by including one additional absorber unit for improving biogas upgrading efficiency. The performance of the biogas upgrading system was evaluated and compared in terms of methane recovery, methane content in biomethane, and energy consumption. Effects of operating conditions such as operating pressure in absorber, concentration, and total flow rate of absorbents were investigated. The results revealed that the performance of the modified absorption system was superior to the conventional system. The methane content in biomethane, methane recovery, and energy consumption increased with the increase of operating pressure in the absorbers. Increasing concentration and total flow rate of absorbents increased the methane content in biomethane and the energy consumption but decreased the methane recovery. The optimal operating condition could achieve 96%v/v of methane content in biomethane with methane recovery of higher than 95%v/v in the modified water absorption system. The optimum operating pressures of absorber Units 1 and 2, and total absorbent flow rates were at 13 and 5 bar and 16,000 kmol/h, respectively.     

Syngas production by non-catalytic reforming of biogas with steam addition under filtration combustion mode

Biogas conversion to syngas (mainly H₂ and CO) is considered an upgrade method that yields a fuel with a higher energy density. Studies on syngas production were conducted on an inert porous media reactor under a filtration combustion mode of biogas with steam addition, as a non-catalytic method for biogas valorization. The reactor was operated under a constant filtration velocity of 34.4 cm/s, equivalence ratio of 2.0, and biogas concentration of 60 vol% Natural Gas/40 vol% CO₂, while the steam to carbon ratio (S/C) was varied between 0.0 and 2.0. Total volumetric flow remained constant at 7 L/min. Combustion wave temperature and propagation rate, product gas composition, reactants conversion as well as H₂ and CO selectivity were measured as a function of S/C ratio. Chromatographic parameters, method validation and measurement uncertainty were developed and optimized. It was observed that S/C ratio of 2.0 gave optimal results under studied conditions for biogas conversion, leading to maximum concentrations of 10.34 vol% H₂, 9.98 vol% CO and highest thermal efficiency of 64.2% associated with a modified EROI of 46.3%, which considered energy consumption for steam supply. Conclusions indicated that the increment of the steam co-fed with the reactants favored the non-catalytic conversion of biogas and thus resulted in an effective fuel upgrading.     

Hydrogen energy deployment in decarbonizing transportation sector using multi-supply-demand integrated scenario analysis with nonlinear programming — A Shanxi case study

Peaking CO₂ emissions and reaching carbon neutrality create a major role for hydrogen in the transportation field where decarbonization is difficult. Shanxi, as a microcosm of China in the systematic transformation of energy end-use consumption, is selected to investigate the hydrogen energy development forecast for decarbonization in the transportation sector. Multi-supply-demand integrated scenario analysis with nonlinear programming (NLP) model is established to analyze hydrogen energy deployment in varied periods and regions under minimum environmental, energy and economic objectives, to obtain CO₂ emission reduction potential. Results reveal that green hydrogen contributes most to low-carbon hydrogen development strategies. In high-hydrogen demand scenarios, carbon emission reduction potential is significantly higher under environmental objectives, estimated at 297.68 × 10⁴–848.12 × 10⁴ tons (2025–2035). The work provides a strategy to forecast hydrogen energy deployment for transportation decarbonization, being of vital significant guide for planning of hydrogen energy transportation in other regions.     

Combined Hydrogen,Heat and Power (CHHP) pilot plant design

The Combined Hydrogen, Heat and Power (CHHP) system consists of a molten carbonate fuel cell, DFC300. DFC300 consumes biogas, and produces electricity and hydrogen. The high temperature flue gas can be recovered for useful purposes. During the hydrogen recovery process, the anode exhaust gas (37.1% H₂O, 45.9% CO₂, 5.7% CO, and 11.2% H₂) is sent through a water gas shift (WGS) reactor to increase the hydrogen and carbon dioxide composition, and then water is removed in a vapor–liquid separator. The remaining hydrogen and carbon dioxide mixture gas is separated using a 2-adsorber pressure swing adsorption unit under 1379 kPa. Resulting hydrogen can achieve 99.99% purity, and it can be stored in composite hydrogen storage tanks pressurized at 34,474 kPa. Hydrogen is produced at a rate of 2.58 kg/h. The produced hydrogen is filled into transportable hydrogen cylinders and trucked to a residential community 7.5 km away from the CHHP site. The community is powered by fuel cells to supply electricity to approximately 51 apartments. A heat recovery unit to produce steam and hot water recovers hot air exhaust from the DFC300, having a total heating value of 405 MJ/h. The greenhouse employs a two-phase steam heating system. Hot water supply is mainly needed for the CHHP education center. DFC300 produces electricity at a maximum capacity of 280 kW. A substation is built to set up the interconnections. Power poles and power lines are built to distribute electricity to the CHHP system, the education center, and the greenhouse. The overall electricity consumption of the CHHP system is 86 kW, and the greenhouse consumes 40 kW. Therefore, an aggregate of 154 kW of power can be used to provide power to the UC Davis campus.     

铂基催化剂快速部分催化氧化甲烷的研究

以Al 2O 3为载体,采用浸渍法制备Pt/Al 2O 3催化剂,通过测量重整反应过程中催化剂的温度分布情况,研究了改变甲烷快速部分氧化重整反应中反应条件(反应气体预混合温度、N 2体积比例、CH 4/O 2比)对反应物的转化率及产物选择性的影响。研究发现,催化剂床层温度的上升可以促进CH 4的转化,使H 2和CO的选择性升高且H 2与CO的物质的量的比(简称H 2/CO比,依此类推)升高。N 2体积比例及CH 4/O 2比的升高,会降低催化剂床层温度,进一步造成CH 4的转化率和H 2/CO比降低,但与仅降低混合气预热温度不同的是,提高N 2体积比例及CH 4/O 2比会造成H 2和CO的选择性升高,这可能是催化剂表面的活性氧导致的。通过对甲烷在Pt催化剂上的反应机理进行了初步讨论,认为甲烷的快速部分催化氧化反应为多种反应路径共存,不同的反应条件下各种反应路径所占比例会发生变化。     

Biogas quality upgrade by simultaneous removal of CO2 and H2S in a packed column reactor

Biogas from anaerobic digestion of biological wastes is a renewable energy resource. It has been used to provide heat, shaft power and electricity. Typical biogas contains 50–65% methane (CH₄), 30–45% carbon dioxide (CO₂), moisture and traces of hydrogen sulphide (H₂S). Presence of CO₂ and H₂S in biogas affects engine performance adversely. Reducing CO₂ and H₂S content will significantly improve quality of biogas. In this work, a method for biogas scrubbing and CH₄ enrichment is presented. Chemical absorption of CO₂ and H₂S by aqueous solutions in a packed column was experimentally investigated. The aqueous solutions employed were sodium hydroxide (NaOH), calcium hydroxide (Ca(OH)₂) and mono-ethanolamine (MEA). Liquid solvents were circulated through the column, contacting the biogas in countercurrent flow. Absorption characteristics were examined. Test results revealed that the aqueous solutions used were effective in reacting with CO₂ in biogas (over 90% removal efficiency), creating CH₄ enriched fuel. H₂S was removed to below the detection limit. Absorption capability was transient in nature. Saturation was reached in about 50 min for Ca(OH)₂, and 100 min for NaOH and MEA, respectively. With regular replacement or regeneration of used solutions, upgraded biogas can be maintained. This technique proved to be promising in upgrading biogas quality.     

基于Ni/Al2O3整体式催化剂的生物质气化合成气甲烷化研究

以生物质气化模拟合成气H2/CO/N2为原料气,以堇青石蜂窝陶瓷为基体制备Ni/Al2O3整体式催化剂,通过扫描电镜(SEM)、比表面积(BET)、X射线衍射(XRD)、程序升温反应法(TPR)、热重分析(TG)等表征分析手段,考察催化剂制备方法(浸渍法和溶胶-凝胶法)、温度(250~550℃)及空速GHSV(6000~14000 mL/(g·h))对催化剂甲烷化性能的影响。结果表明:浸渍法制备的Ni/Al2O3催化剂(DIP-Ni/Al2O3)与溶胶-凝胶法制备的Ni/Al2O3催化剂(SGNi/Al2O3)相比,前者甲烷化性能较好。在H2、CO、N2物质的量之比为3∶1∶1且空速为10000 mL/(g·h)条件下,浸渍法制备的Ni/Al2O3催化剂在400℃时甲烷化性能最佳,且该条件下CO转化率为98.6%,CH4选择性为90.9%。当H2、CO、N2物质的量之比为3∶1∶1且温度为400℃时,在实验空速范围内,浸渍法制备的Ni/Al2O3催化剂CO转化率和CH4选择性均基本稳定在90%,甲烷化性能较好。