纳米粒子对CO2水合物导热性能的影响

试验研究了不同种类（Al₂O₃、Cu、SiO₂）、不同质量分数（0.05%、0.1%、0.15%）及不同粒径（10、30、50 nm）的纳米粒子对CO₂水合物热导率的影响。结果表明温度为-5~5℃时,纯CO₂水合物热导率为0.553~0.5861 W·m^-1·K^-1,具有玻璃体的变化特性。分散剂SDBS的加入,可改善CO₂水合物-纳米粒子体系的导热性能。在相同的质量分数和粒径下,纳米Cu粒子对CO₂水合物热导率的增强作用最好,但综合考虑水合物生成特性和溶液悬浮稳定性,选用纳米Al₂O₃粒子较合适。Al₂O₃粒子粒径越小,水合物热导率越大,15 nm比50 nm纳米粒子体系中CO₂水合物热导率的增长率平均提高了12.7%。此外,CO₂水合物热导率随Al₂O₃粒子质量分数的增大而增大,质量分数由0.05%增加到0.15%时,水合物热导率的增长率由4.2%提高到8.2%。     

寒冷地区CO2空气源热泵供暖运行性能分析

CO₂空气源热泵能够在寒冷地区低温环境下稳定运行,可望在建筑供暖领域推广应用。为客观、合理地评价CO₂空气源热泵供暖的运行性能,搭建了寒冷地区超临界CO₂空气源热泵供暖系统。根据室外环境温度和供暖热负荷将供暖期划分为5个不同的阶段,分阶段调整CO₂空气源热泵供暖运行参数。测试结果表明,CO₂空气源热泵能够满足寒冷地区供暖需求,且供暖系统在供暖季的平均性能系数可达2.236,同时供暖房间具有较好的舒适度。以燃煤锅炉、燃气锅炉为参照,采用等效电方法对比分析了三种热源供暖的能源利用效率及CO₂排放量。对比分析结果表明,在考虑能源品位之后,CO₂空气源热泵供暖的能源利用效率高于燃气锅炉供暖,略低于燃煤锅炉供暖。受燃料含碳量的影响,CO₂空气源热泵供暖的CO₂排放量虽然高于燃气锅炉供暖,但比燃煤锅炉供暖减少20.89%。     

充注压力对压缩式制冷循环连续制备CO2水合物的影响

研制了一台能够连续制备蓄冷用CO₂水合物的压缩式循环实验装置,并在该装置上研究了充注压力对水合物的预冷时间、生成质量、水合比例和潜热蓄冷量的影响。实验结果表明水合物在CO₂气泡上升过程中生成,在气液界面处堆积。高的充注压力有着更理想的蓄冷特性,当充注压力为4.2 MPa时,预冷时间为8 min、水合物生成质量为8.44 kg、水合比例为75.1%、水合物潜热蓄冷量为4.22 MJ。充注压力为3.8 MPa及以上时,水合物生成量大,水合物阻碍釜内各部分的传热,使釜内中层、下层的温差较大。水合物生成过程后期,水合放热量减少,液体CO₂在反应釜内的蒸发吸热效应使得釜内温度继续降低,一直到低于0℃,充注压力越高,此现象越明显。     

球霰石型纳米碳酸钙椭球形颗粒的合成

以氧化钙为原料,在非水体系下采用二氧化碳碳化法制备球霰石型纳米碳酸钙椭球形颗粒。探究了碳化温度、氧化钙用量、二氧化碳流速和溶剂种类对纳米碳酸钙晶型、颗粒形貌的影响,并优化了工艺条件。采用XRD、SEM、FT-IR和TEM等对产物进行表征,并探讨了合成机理。结果表明：4个因素对纳米碳酸钙的形貌均有影响,碳化温度对晶型影响较大。以甲醇作为溶剂和模板,当碳化温度为5 ℃,氧化钙用量为2.8 g（每100 mL甲醇）,二氧化碳流速为100 mL/min时,可制得球霰石型纳米碳酸钙椭球形颗粒。     

Feasibility analysis and process simulation of CO2 dehydration using triethylene glycol for CO2 pipeline transportation

The operation of dehydration is very important in the process of gas transportation. This study aims to evaluate the application feasibility of CO₂ dehydration using triethylene glycol, which is also called TEG for short. Aspen Plus software was used to simulate the dehydration process system of CO₂ gas transportation using TEG dehydration. Parameter analysis and process improvement were carried out for the simulation of dehydration process. At first, a sensitivity analysis was conducted to analyze and optimize operating conditions of conventional CO₂-TEG dehydration process system. Subsequently, a recycle unit was introduced into the conventional CO₂-TEG dehydration process system, it can be found that the improved process system with the recycle unit has a higher CO₂ recovery rate which was about 9.8% than the conventional one. Moreover, the improved process system showed excellent operation stability through the comparison of simulation results of several processes with various water contents in their feed gases. Although the energy consumption is increased by about 2%, the improved process was economically and technically feasible for the long-term availability of CO₂ pipeline transportation. The simulated results showed that the improved CO₂-TEG process system has promising application prospects in CO₂ dehydration of CO₂ gas transportation with high stability.     

Energy efficiency analysis of natural gas hydrates production method

The decomposition of natural gas hydrates is a phase change process, which involves the consumption and conversion of various forms of energy, such as electrical energy, chemical energy, and thermal energy. In order to evaluate the economy capacity of natural gas hydrates exploitation, an exergy model was established to calculate the energy efficiency ratio (EER) of hydrate production method. The CO₂ replacement method is taken as a case study to introduce the calculation equation and flow chart of energy efficiency ratio in any production period. The amount of CO₂ injection, gas production and mole fraction of methane in produced gas are three key parameters in the process of CO₂ replacement. The ratio between the amount of gas production and CO₂ injection is defined as production injection ratio to eliminate the influence of deposit size. This work studied the influence of production injection ratio and the mole fraction of methane in produced gas on EER. The results show that the EER of gas hydrates production by CO₂ replacement is between 0.31 and 6.4 under the set conditions, and it increases with the increase of production injection ratio. In addition, increasing the mole fraction of methane in produced gas can reduce the energy consumption for gas separation and increase EER. Therefore, there are two effective ways to increase EER of CO₂ replacement through controlling the amount of gas production and the mole fraction of methane in produced gas. The EER model is established to provide guidance for the optimization of gas hydrate mining process.     

天然气水合物置换开采的能源效率研究

天然气水合物分解是一个相变过程，开采时涉及各种形式能量的消耗和转化，如电能、化学能、热能等。为了科学地评价天然气水合物开采技术的经济性，建立了以有效能（）为核心的能源效率计算方程，并以CO₂置换法开采天然气水合物为例，介绍任意生产周期内能源效率的计算方法和流程框图。在CO₂置换开采天然气水合物的工艺过程中，注气量、产气量和产气中甲烷含量是三个关键参数，将产气量与注气量之比定义为采注比，分析采注比及产气中甲烷含量对能源效率的影响。结果表明：在设定条件下CO₂置换开采天然气水合物的整体能源效率介于0.31～6.4之间；增大采注比，有利于提高能源效率；产气中甲烷的摩尔分率越高，气体分离的能耗越低，能源效率也可显著提高。因此，调控产气量和产气中甲烷摩尔分率是提高CO₂置换法能源效率的主要途径。通过所建立的能效计算方程为天然气水合物开采工艺的优化提供指导。     

CO2浓度对混溶态(CO2+正己烷)/盐水界面微观特性的影响

在CO₂以超临界状态封存于油气藏时,储层中流体间的界面性质是影响封存效率和封存量的重要因素。利用分子动力学模拟的方法,对330 K、20 MPa混溶条件下(CO₂+正己烷)/NaCl溶液系统的界面微观性质进行了研究,分析了混溶相中CO₂摩尔分数变化时,界面处CO₂和正己烷的亲水、疏水特性及其影响,为CO₂地质封存提供理论依据。研究发现,随着混溶相中CO₂摩尔分数的增加,界面厚度及粗糙度增大,分子渗透加深,热波动加剧。界面上CO₂与水之间更强的相互作用造成了CO₂注入过程中界面张力的降低。CO₂表现出类似于表面活性剂的性质,并在CO₂摩尔分数为65%(质量分数为50%)时,其界面累积量以及正己烷的驱离量最大。界面处存在特殊的分子微观结构,CO₂、水及正己烷分子呈现特殊的排布方式。     

跨临界二氧化碳热泵喷射循环实验

在跨临界CO₂热泵热水器系统中引入优化设计的喷射器,对系统进行实验研究,分析了制热系数、引射比、升压比、喷射器效率等参数随热水体积流量和出口温度及高压侧压力的变化趋势以及优化设计的喷射器对系统的影响。实验结果表明:随着热水体积流量减小或其出口温度增加,引射比将逐渐减小,而喷射器效率逐渐升高;在测试工况范围内升压比基本保持不变,系统COP_h最高将近3.5;系统高压侧的压力因优化喷射器的引入而明显降低,有利于系统的安全运行;跨临界二氧化碳热泵喷射循环系统存在一个最优运行压力,值得注意的是在最优运行压力下,热水出水温度虽未达到最高,但依旧超过55℃。系统稳定运行在最优高压侧压力下,不仅系统性能大幅度提高,而且保证了热水的出水温度。     

基于二氧化碳、水、太阳能的绿色化工精炼

化石资源为人类提供了不可或缺的化学品、材料以及燃料,但也造成了大量二氧化碳排放。生物质是可以生产低碳化工产品的可再生资源,但要占用有限的可耕地资源。提出了直接以二氧化碳、水和太阳能为原料的绿色化工精炼。采用光电板收集太阳能并转化为电能,电能通过膜式水电解池产生氢气,氢气通入新型生物反应器并在自养菌的作用下把二氧化碳还原为聚三羟基丁酸酯(PHB)。此新型生物反应器解决了因气体溶解性低而影响传质速度的关键技术,微生物干重产出达0.18 g·L^-1·h^-1,其中PHB质量分数约50%。PHB不仅是优良的可生物降解塑料,也是可用于生产C₃～C₄有机低分子和芳香烃的平台化合物。在磷酸催化作用下,PHB可转化为与汽油相当热值和元素组成的C₄～C₁₆燃料油。分离PHB后的细菌生物质残渣可水热分解获得生物油和富氮水相产物。此生物油具有比植物生物油更高的热值,而水相产物可作为营养物用于培养微生物。     

Investigation of the hydrate formation process in fine sediments by a binary CO2/N2 gas mixture

To obtain the fundamental data of CO₂/N₂ gas mixture hydrate formation kinetics and CO₂ separation and sequestration mechanisms, the gas hydrate formation process by a binary CO₂/N₂ gas mixture (50:50) in fine sediments (150-250 μm) was investigated in a semibatch vessel at variable temperatures(273, 275, and 277 K)and pressures (5.8-7.8 MPa). During the gas hydrate reaction process, the changes in the gaseous phase composition were determined by gas chromatography. The results indicate that the gas hydrate formation process of the binary CO₂/N₂ gas mixture in fine sediments can be reduced to two stages. Firstly, the dissolved gas containing a large amount of CO₂ formed gas hydrates, and then gaseous N₂ participated in the gas hydrate formation. In the second stage, all the dissolved gas was consumed. Thus, both gaseous CO₂ and N₂ diffused into sediment. The first stage in different experiments lasted for 5-15 h, and >60% of the gas was consumed in this period. The gas consumption rate was greater in the first stage than in the second stage. After the completion of gas hydrate formation, the CO₂ content in the gas hydrate was more than that in the gas phase. This indicates that CO₂ formed hydrate easily than N₂ in the binary mixture. Higher operating pressures and lower temperatures increased the gas consumption rate of the binary gas mixture in gas hydrate formation.     

CO2在ZIF-8/乙二醇-2-甲基咪唑浆液中溶解能力理论分析

有效降低CO₂排量实现碳中和是当前研究热点之一。ZIF-8/乙二醇-2-甲基咪唑浆液被发现不仅能高效地捕集CO₂,同时能利用浆液良好的流动性实现一个碳捕集-浆液流动再生-浆液再利用的连续碳捕集过程。为了有效地掌握纯CO₂气体在ZIF-8/乙二醇-2-甲基咪唑浆液中的溶解能力,本文首先测定了293.15K、303.15K和313.15K下CO₂在干ZIF-8上的吸附量和在2-甲基咪唑-乙二醇溶液中的溶解性;然后基于Langmuir方程和CO₂溶解机理进一步建立了相应吸附量和溶解度计算数学模型;最后综合考虑ZIF-8/乙二醇-2-甲基咪唑浆液中乙二醇和ZIF-8之间的共存特征和相互影响,建立了CO₂在目标浆液中溶解吸收量计算数学关联式。所得研究结果对浆液法CO₂技术的推广和后续流程模拟具有良好的指导作用和理论意义。     

富氧燃烧烟气压缩净化及高浓度CO2制备工艺研究

富氧燃烧技术是目前最有可能大规模推广和商业应用的碳捕集与封存技术之一,其中,烟气压缩净化及CO₂提纯对于整个富氧燃烧系统至关重要。然而,目前研究多聚焦于富氧燃烧后烟气压缩净化的工艺验证,而对烟气压缩纯化各单元运行特性的研究仍不深入,特别是烟气压缩净化过程杂质污染组分的迁移转化、系统运行参数与污染物脱除效率的关联仍不明确。且现有研究对净化后烟气的深度提纯及高浓度CO₂制备的关注也相对较少,直接关系到富氧燃烧系统运行经济性。因此,针对富氧燃烧烟气净化及CO₂提纯需求,系统探究了富氧燃烧烟气压缩纯化过程SO₂、NO_x吸收脱除以及CO₂深度提纯等各子系统的运行特性,其中SO₂与NO_x脱除采用压缩-酸液吸收,CO₂深度提纯采用低温精馏。结果表明:通过烟气净化可实现SO₂脱除效率达100%,NO脱除效率达99%,同时实现纯度为99.99%的食品级液态CO₂制备。烟气净化过程中,气相反应占据主导,提高压力可缩短反应时间;当SO₂吸收塔运行压力超过0.8 MPa时,SO₂脱除效率可达100%;当NO吸收塔运行压力超过3.0 MPa时,NO排放浓度可达超低排放标准。CO₂提纯过程中,提高压力会降低液体CO₂纯度。SO₂吸收塔运行压力为1.6 MPa、NO吸收塔运行压力为3.0 MPa、CO₂提纯塔运行压力为3.8 MPa时,系统整体功耗最低,为0.37 MJ/kg。     

Ni/Al_2O_3催化剂的CO_2-TPD表征

Ni/Al_2O_3催化剂是甲烷二氧化碳重整反应制取合成气研究最多、最具应用潜力的一种催化剂。通过对催化剂进行CO_2-TPD研究,考察还原态Ni/Al_2O_3催化剂的CO_2脱附特性。结果表明,浸渍法制备的Ni/Al_2O_3催化剂CO_2脱附曲线呈现双峰,分别在(60~65)℃和(350~380)℃出现高低温两个活性位;高温CO_2吸附量为3.0 cm~3·g~(-1),低温CO_2吸附量为24.0 cm~3·g~(-1)。催化剂的CO_2吸附量与其Ni含量无关。考察选用不同载体的CO_2脱附行为,发现以Al_2O_3为载体的催化剂CO_2吸附量是MgO和SiO_2为载体催化剂的2~4倍,以TiO_2为载体的催化剂几乎不吸附CO_2。     

Na2CO3基吸附剂颗粒制备及其脱碳性能

采用挤压-滚圆法制备Na₂CO₃基CO₂吸附剂微球颗粒,在自行设计的CO₂吸收系统中对制备的样品进行脱碳性能测试。结合相关表征测试,探明不同载体、不同负载量的Na₂CO₃基吸附剂的微观结构、脱碳性能以及机械性能的变化规律和内在原因。研究表明：不同载体的Na₂CO₃基吸附剂颗粒脱碳性能存在明显差异,其中氧化铝负载的吸附剂（Na₂CO₃/Al₂O₃）的脱碳性能最好,可达1.14mmol/g。铝酸钙水泥负载的吸附剂（Na₂CO₃/CA）机械性能较好,但其脱碳性能最差。结合吸附剂脱碳和机械性能的综合考量,Na₂CO₃/Al₂O₃是最为合适的CO₂吸附剂,并进一步研究不同Na₂CO₃负载量的影响。研究发现随着Na₂CO₃负载量的变化,吸附剂的微观结构、脱碳性能以及机械性能都存在明显的差异。虽然60%负载量的Na₂CO₃/Al₂O₃吸附剂颗粒的机械性能和脱碳效果较好,但其成球度较差,影响其实际应用。质量分数40%负载量的Na₂CO₃/Al₂O₃吸附剂颗粒具有良好的脱碳性能、机械性能以及成球度,CO₂脱除量为1.36mmol/g。总体而言,利用挤压-滚圆法制备的Na₂CO₃基吸附剂颗粒具有良好的流动特性、脱碳性能和机械性能,适用于电厂烟气中的CO₂脱除。     

Phase behavior of the perfluoropolyether microemulsion in supercritical CO2 and their use for the solubilization of ionic dyes

Phase behavior of the perfluoropolyether surfactant microemulsion in supercritical CO₂ and the solubilization of conventional ionic dyes in the same system have been investigated using Perfluoro 2,5,8,11-tetramethyl-3,6,9,12-tetraoxapentadecanoic acid ammonium salt. We found that the surfactant prepared in this study was satisfactorily dissolved in supercritical CO₂ without the presence of entrainer. Moreover dissolved surfactant had an ability to form micellar aggregates and to incorporate a small amount of water in the interior of aggregates. We also found that conventional ionic dyes such as acid dye, reactive dye and basic dye were solubilized in the microemulsion system in supercritical CO₂.     

褐煤热解-气化-制油系统的CO2减排策略

褐煤热解-气化-制油系统是现代煤化工发展的一个重要研究内容。来自系统多个单元产生的CH₄和CO₂如果发生重整反应,将重整得到H₂/CO比值较高的合成气添加到制油流程中,可实现更多的C被固定到产品中而减少CO₂的直接排放量。对CH₄-CO₂和CH₄-H₂O两种重整反应方式、来自煤热解和费托合成两股甲烷气和典型的干粉气化和水煤浆气化两种流程进行了组合研究。分析结果显示,来自热解和费托合成的甲烷重整后不足以提供调节合成气H₂/CO比例所需的氢气,水煤气变换反应对于褐煤制油系统来说是必需的。从C转化成油的角度来看,采用干粉气化和CH₄-H₂O重整的方案是较好的选择。     

Influence of CO-evolving groups on the activity of activated carbon fiber for SO2 removal

An investigation was made into the influence of CO-evolving and CO₂-evolving groups on the activities of activated carbon fibers (ACFs) for the oxidative conversion of SO₂ into aq. H₂SO₄ in the presence of O₂ and H₂O. The results indicated that the amount of evolved CO determined the SO₂ removal activity of ACFs, whereas, the amount of evolved CO₂ did not correlate with the ACFs activity for SO₂ removal. A direct proportionality between the amount of evolved CO and the enhanced activity of SO₂ removal was confirmed by using different oxidizing agents for changing the types and amount of oxygen functional groups in ACFs.     

The impact of connate water saturation and salinity on oil recovery and CO2 storage capacity during carbonated water injection in carbonate rock

Carbonated water injection (CWI) is known as an efficient technique for both CO₂ storage and enhanced oil recovery (EOR). During CWI process, CO₂ moves from the water phase into the oil phase and results in oil swelling. This mechanism is considered as a reason for EOR. Viscous fingering leading to early breakthrough and leaving a large proportion of reservoir un-swept is known as an unfavorable phenomenon during flooding trials. Generally, instability at the interface due to disturbances in porous medium promotes viscous fingering phenomenon. Connate water makes viscous fingers longer and more irregular consisting of large number of tributaries leading to the ultimate oil recovery reduction. Therefore, higher in-situ water content can worsen this condition. Besides, this water can play as a barrier between oil and gas phases and adversely affect the gas diffusion, which results in EOR reduction. On the other hand, from gas storage point of view, it should be noted that CO₂ solubility is not the same in the water and oil phases. In this study for a specified water salinity, the effects of different connate water saturations (S_wc) on the ultimate oil recovery and CO₂ storage capacity during secondary CWI are being presented using carbonate rock samples from one of Iranian carbonate oil reservoir. The results showed higher oil recovery and CO₂ storage in the case of lower connate water saturation, as 14% reduction of S_wc resulted in 20% and 16% higher oil recovery and CO₂ storage capacity, respectively.