CO2 capture in a multistage CFB: Part II: Riser with multiple cooling stages

A 1 m in diameter and 3.55 m tall fluidized bed riser internally with water tubes, which required six equilibrium stage of riser‐sorber for capturing about 95% of CO₂ emitted from a coal power plant, were designed to replace the multisingle risers. At the optimum operating condition, the temperature of the cooling tubes in the bottom, the middle and the top of the riser were kept constant values at 50, 40, and 30°C, respectively. The hot water (57°C) from lowest exchanger section can be used to preheat the spent sorbent for the regeneration in a downer. The rest of the heat for the regenertion is obtained from the stack gas (100–130°C). This new concept promises to reduce the energy consumption for CO₂ removal from flue gas. The only energy requirement is for pumping fluid and fluidizing particles in the bed. © 2017 American Institute of Chemical Engineers AIChE J, 63: 5280–5289, 2017     

用于燃烧后CO2捕集系统的胺基固态吸附材料研究进展

随着工业化的发展和大量化石燃料的消耗,大量的CO₂气体排放到大气中并引发了一系列严重的环境问题,而采用燃烧后CO₂捕集技术可以有效地应对这一问题。寻找一种高效吸附、稳定、价格低廉的固态吸附材料对于开展燃烧后CO₂捕集系统的研究具有重要的实际意义。近年来,胺基固态吸附材料因其高CO₂吸附能力和高吸附选择性成为研究的热点。本文综述了近年来国内外学者对不同胺基固态吸附材料在合成方法、载体材料选择以及性能测试等方面进行的研究,重点讨论了以沸石分子筛、介孔硅分子筛、多孔碳和金属有机骨架为载体的胺基固态吸附材料对CO₂的吸附行为,并指出多孔载体材料的结构改进及有机胺和促进剂的合理选择将会成为未来胺基固态吸附材料的重点研究方向。     

Carbon dioxide capture using solid sorbents in a fluidized bed with reduced pressure regeneration in a downer

The most common technology for postcombustion CO₂ capture for existing power plants is the amine solvent scrubber. The energy consumption for capturing CO₂ from flue gases using amine solvent technology is 15 to 30% of the power plant electricity production. Hence, there is a need to develop more efficient methods of removing CO₂. Here, we show a novel design, obtained using multiphase CFD, and of a fluidized‐bed reduced pressure regenerator, coupled with a fluidized‐bed sorber, which has the potential to reduce the energy consumption. The undesirable core‐annular flow regime in the riser‐sorber is eliminated using multiple jet inlets and large particles leading to a shorter height. Up to 88% of the heat liberated in the riser‐sorber is recovered in the downer‐regenerator. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4519–4537, 2013     

镁负载CaO基吸附剂捕集CO2性能及抗烧结机理

复合钙基吸附剂制备成本过高是限制其工业化应用的主要瓶颈问题。本文以不可溶的CaCO₃和Ca(OH)₂作为钙源,通过燃烧合成法制备钙镁复合吸附剂,在双固定床反应器上研究了其循环捕集CO₂性能。结果显示：制备得到的钙镁复合吸附剂具有更发达的孔隙结构,吸附剂表面Ca和Mg分散均匀,MgO均匀分布于CaO晶粒之间,有效提高了钙镁复合吸附剂的抗烧结特性,因此钙镁复合吸附剂循环反应过程中具有高捕集CO₂活性。以Ca(OH)₂作为钙源时,燃烧合成过程中Ca和Mg均匀同时析出,分散更加均匀,有效避免了CaCO₃作为钙源时Mg的团聚问题,因此得到的钙镁复合吸附剂循环捕集CO₂性能最优。最佳的Ca/Mg摩尔比为(8∶2)~(7.5∶2.5)。本研究以不可溶钙源制备得到高活性钙镁复合吸附剂,有效控制了吸附剂成本,具有更好的工程应用前景。     

Application of engineered natural ores to intermediate- and high-temperature CO2 capture and conversion

Integrated CO₂ capture and conversion (ICCC) is a promising technology aiming at converting waste CO₂ to fuels and high value-added chemicals. Herein, we described a proof-of-concept study of applying engineered natural ores (dolomite, magnesite, and limestone) to two different ICCC processes—intermediate-temperature ICCC for CH₄ production (350–400°C) and high-temperature ICCC for syngas production (650–700°C). In the former process, a MgO-based CO₂ sorbent prepared from dolomite and magnesite was combined with a methanation catalyst in a dual-bed configuration, whereby a CH₄ yield of 7.1–7.3 mmol/g can be stably achieved per cycle over 20 consecutive ICCC cycles. In the latter process, a CaO-based sorbent derived from dolomite and limestone was coupled with a reforming catalyst also in a dual-bed mode, whereby syngas with a H₂/CO ratio of 0.9–1.0 can be produced over 20 cycles. This study will expand the application of natural ores in CO₂ emission reduction.     

氨基修饰复合型钠基吸收剂的脱碳特性

为弥补常规钠基吸收剂活性差、脱碳量低的不足,制备了多种表面氨基修饰的新型复合型钠基吸收剂并研究其脱碳特性。通过比较氨基流失率和实际脱碳量,选定二氧化硅的前驱物正硅酸乙酯为载体前驱物,以碳酸钠为活性成分,分别以3-氨基丙基三甲氧基硅烷(APS)、3-氨基丙基三乙氧基硅烷(APTES)、二乙烯三胺(DETA)、三乙烯四胺(TETA)为氨基前驱物,制备得到多种表面氨基修饰的复合型钠基吸收剂。探究各种吸收剂的孔隙结构与脱碳特性,结果表明,APS、APTES修饰后吸收剂孔隙特性较差,脱碳量较低,DETA、TETA修饰后吸收剂孔隙结构得到改善,脱碳量较高。     

基于钠基吸附剂的烟气脱碳系统余热利用研究

针对基于钠基固体吸附剂的燃烧后脱碳技术应用于燃煤电厂后综合能耗偏高的问题,本文提出与供热机组结合的碳捕集/供热双机组系统,利用低温热网回水回收系统低品位余热。依据双机组的抽汽混合与否构建了两种系统流程,分析了两种不同方案下的系统性能。研究结果表明,在有效回收脱碳系统碳酸化反应余热后,独立抽汽方案中碳捕集综合能耗从4.05GJ/t CO₂降低至1.26GJ/t CO₂,而混合抽汽方案中碳捕集综合能耗降低至1.13GJ/t CO₂,同时双机组系统的热网供热量较单供热机组分别增加了67.5%和72.8%,经济效益显著。分析了混合抽汽方案的系统中碳捕集综合能耗随相关运行参数变化的规律,发现碳酸化反应温度和热网回水温度因为能够直接影响系统余热利用程度因而更易对碳捕集综合能耗产生影响。     

Theoretical and experimental study on the fluidity performance of hard-to-fluidize carbon nanotubes-based CO2 capture sorbents

Carbon nanotubes-based materials have been identified as promising sorbents for efficient CO₂ capture in fluidized beds, suffering from insufficient contact with CO₂ for the high-level CO₂ capture capacity. This study focuses on promoting the fluidizability of hard-to-fluidize pure and synthesized silica-coated amine-functionalized carbon nanotubes. The novel synthesized sorbent presents a superior sorption capacity of about 25 times higher than pure carbon nanotubes during 5 consecutive adsorption/regeneration cycles. The low-cost fluidizable-SiO₂ nanoparticles are used as assistant material to improve the fluidity of carbon nanotubes-based sorbents. Results reveal that a minimum amount of 7.5 and 5 wt% SiO₂ nanoparticles are required to achieve an agglomerate particulate fluidization behavior for pure and synthesized carbon nanotubes, respectively. Pure carbon nanotubes + 7.5 wt% SiO₂ and synthesized carbon nanotubes + 5 wt% SiO₂ indicates an agglomerate particulate fluidization characteristic, including the high-level bed expansion ratio, low minimum fluidization velocity (1.5 and 1.6 cm·s^–1), high Richardson−Zakin index (5.2 and 5.3 > 5), and low Π value (83.2 and 84.8 < 100, respectively). Chemical modification of carbon nanotubes causes not only enhanced CO ₂ uptake capacity but also decreases the required amount of silica additive to reach a homogeneous fluidization behavior for synthesized carbon nanotubes sorbent.     

二氧化碳捕集技术及应用分析

分析了CO2捕集技术及现状。CO2捕集是CCS的关键技术单元之一,针对不同的CO2气源,国内外研究开发了多种技术。许多CO2捕集技术已经工业化,其中燃烧后烟气中CO2的捕集技术主要是以一乙醇胺(MEA)为基础的胺法;燃烧前的CO2捕集技术主要应用于IGCC电厂,一般需要对煤气中CO进行部分变换,变换后脱碳可采用成熟技术,如Selexol(NHD)等。富氧燃烧则是在中试成功的基础上,进行更大规模的工业示范。国内外大型煤制油化工项目主要采用低温甲醇洗脱除CO2,如果设置CO2产品塔,则可以获得体积分数98%以上的CO2。天然气脱碳主要采用MDEA技术。另外还有低温法、PSA、膜分离等CO2捕集技术及化学链燃烧等一些正在研发的技术。     

Development of a Scalable Method for Manufacturing High‐Temperature CO2 Capture Sorbents

An engineered process for scalable manufacture of a calcium aluminum carbonate CO₂ sorbent with production amounts of about 1000 g per hour has been developed. The process includes mixing and heating, solid‐liquid separation, drying and extrusion, crushing and conveying, and calcined molding steps. The sorbent preparation involves the coprecipitation of Ca²⁺, Al³⁺, and CO₃^2– under alkaline conditions. By adjusting the Ca:Al molar ratio, a series of Ca‐rich materials could be synthesized for use as CO₂ sorbents at 750 °C. A calcium acetate‐derived sorbent exhibited better cyclic stability than sorbents originating from CaCl₂ and Ca(NO₃)₂. The initial sorption capacity increased with CaO concentration. High stability of more than 90 % was maintained by the Ca:Al sorbents after 40 looping tests.     

CO2 capture by double metal modified CaO-based sorbents from pyrolysis gases

High-temperature pyrolysis technology can effectively solve the problem of municipal solid waste pollution. However, the pyrolysis gas contains a large amount of CO₂, which would adversely affect the subsequent utilization. To address this problem, a novel method of co-precipitation modification with Ca, Mg and Zr metals was proposed to improve the CO₂ capture performance. X-ray diffraction (XRD) patterns and energy dispersive X-ray spectroscopy analysis showed that the two inert supports MgO and CaZrO₃ were uniformly distributed in the modified calcium-based sorbents. In addition, the XRD results indicated that CaZrO₃ was produced by the reaction of ZrO₂ and CaO at high temperatures. The effects of doping ratios, adsorption temperature, calcination temperature, CO₂ concentration and calcination atmosphere on the adsorption capacity and cycle stability of the modified calcium-based sorbent were studied. The modified calcium-based sorbent achieved the best CO₂ capture performance when the doping ratio was 10:1:1 with carbonation at 700 ℃ under 20% CO₂/80% N₂ atmosphere and calcination at 900 ℃ under 100% N₂ atmosphere. After ten cycles, the average carbonation conversion rate of Ca-10 sorbent was 72%. Finally, the modified calcium-based sorbents successfully reduced the CO₂ concentration of the pyrolysis gas from 37% to 5%.     

复合钙基CO2吸收剂的反应性能及显微结构

采用溶胶-凝胶法制备了掺杂La3+、Mg2+的复合钙基CO2吸收剂,并在固定床反应器上进行了多循环的煅烧/碳化实验,对其CO2吸收活性及循环反应稳定性进行了研究.实验结果表明,掺杂La3、Mg2+的复合钙基吸收剂可以显著提高吸收剂在多循环煅烧/碳化过程中的反应活性和循环稳定性.在XRD分析的基础上,计算和比较了不同钙基...     

Synthetic Ca‐based solid sorbents suitable for capturing CO2 in a fluidized bed

Coprecipitation and hydrolysis of CaO have been employed to produce Ca‐based synthetic sorbents suitable for capturing CO₂ in a fluidized bed. Their composition, CO₂ uptake, volume in small pores (2–200 nm) and resistance to attrition were measured and compared to those of limestone and dolomite. Sorbents produced by hydrolysis showed the highest uptake and resistance to attrition. After 20 cycles of carbonation and calcination, two sorbents exceeded the uptake of both limestone and dolomite, when subjected to the same regimes of reaction. A sorbent's uptake of CO₂ was shown to be determined by the volume in pores narrower than ～200 nm.     

Fictitious particle method: A numerical model for flows including dense solids with large size difference

Large solids coexist with small solids in a number of dense gas‐solid flow applications such as fluidized beds and pneumatic conveyers. A new numerical model that is based on the discrete element method–computational fluid dynamics mesoscopic model and extended by introducing an idea appearing in volume penalization method is presented. In computational cells including large and small solids, the amount of momentum exchange between the fluid and the solids is estimated by assuming that a large solid consist of small, dense fictitious particles. We describe the proposed model in detail and show the optimal model parameters found through a number of parameter‐dependency studies. Validation study is performed for the motion of a large sphere in a bubbling fluidized bed and good agreements are confirmed for floating and sinking motions of the sphere between the present model and the experiment. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1606–1620, 2014     

Exploring aramid as emerging contender for CO2 capture

To prevent CO_2 accumulation in the atmosphere generated from scorching of fossil fuels, carbon capture and sequestration(CCS) technology is considered as a potential route to mitigate the emissions of CO_2 from reaching the atmosphere. Power generation from sources such as gas, coal and biomass can fulfill the energy demand more readily than many other sources of electricity production. Thus these sources may be retained as important alternative option in the global energy cycle. In order to curtail CO_2, porous aramid network was fabricated by the condensation of 1,3,5-benzenetricarbonyl trichloride and 1,3-phenylenediamine in 1,4-dioxane solvent. Aramid was characterized for various analyses including FTIR, XRD, TGA, BET surface area and pore size analysis, FESEM and CO_2 adsorption measurements. Excellent thermal stability was provided by strong amide linkages in the polymer backbone. Optimum CO_2 uptake of aramid was achieved to be 23.14 mg·g~(-1) at 273 K at 0.1 MPa. The basic amide groups of network structure showed greater affinity for CO_2.Excellent thermal stability of aramid makes it a promising sorbent for CO_2 capture in adverse conditions.     

溶液燃烧合成法制备自活化钙铜复合CO2吸收剂的性能

首次采用溶液燃烧合成法制备了钙铜复合吸收剂用于实现低成本CO₂捕捉。在热重分析仪上研究制备参数（燃烧背景温度、煅烧时间）对吸收剂循环载氧和CO₂捕捉性能的影响,并借助SEM和氮吸附分析其微观结构。结果表明,在燃烧背景温度800℃、煅烧时间为0.5h时制得的钙铜比例为1∶1的复合CO₂吸收剂15次循环之后,钙基吸收剂转化率为51.2%,比纯的CaO提高了44.9%;采用该方法制备的吸收剂具备自活化特性,15次循环内碳酸化性能随循环次数的增加不降反升,且载氧性能非常稳定,氧化率始终高于90%。微观结构表征表明,随着循环次数的增加,复合吸收剂未发生严重烧结并且BET比表面积没有下降。实验结果为溶液燃烧合成法制备高性能钙铜复合CO₂吸收剂的进一步研究提供了基础数据。     

蒸汽活化钙基吸收剂联合脱碳脱硫特性

利用管式炉（TF）、蒸汽发生器和热重分析仪（TGA）研究了钙基吸收剂联合脱碳脱硫以及水合特性,并通过N2吸附实验对不同烧结程度以及水合前后样品的孔隙结构进行了测量。结果表明,无水合时,40次碳化循环后的样品碳化活性降至18%,但仍具有44%的硫化活性,比新鲜剂仅低4%,说明脱碳失效剂仍是良好的脱硫剂。碳循环失效剂经蒸汽活化后其碳化活性可提高至68%左右,且具有与新鲜剂类似的活性下降规律。每两次碳化循环后进行一次蒸汽活化,可使样品保持65%的平均转化率。蒸汽活化后吸收剂硫化率可提高至80%,远高于新鲜剂,由电镜扫描实验发现这是由于水合时颗粒产生了大的裂缝和破碎,提供了大量产物可自由生长的外表面积。不考虑颗粒磨损,利用钙基吸收剂先循环脱碳再蒸汽活化最后脱硫是一项联合脱除烟气中CO₂和SO₂的新方法。     

Pyrene-based hypercrosslinked microporous resins for effective CO2 capture

Two hydrophobic pyrene-based hypercrosslinked microporous resins (ZLYs) with intrinsic hydroxyl groups on the pore-walls have been prepared by condensation of 1,3,6,8-tetrakis(p-formylphenyl)pyrene (TFPPy) with phloroglucinol (L₁) or 1,5-dihydroxynaphthalene (L₂). The resulting porous networks exhibited high thermal stabilities and moderate Brunauer–Emmett–Teller surface area with 647 and 243 m² g⁻¹ respectively. The experiments showed that the weak interactions between CO₂ and the intrinsic hydroxyl groups on the pore-wall of the resins could enhance CO₂ uptake and CO₂/CH₄ selectivity. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47448.     

多孔液体在CO2捕集与利用领域的研究进展

为助力中国早日实现“双碳目标”,深入落实化工领域绿色低碳可持续发展的重要举措,吸附-吸收耦合有望成为气体分离的绿色变革性分离技术,其关键是高性能吸附（收）材料的开发。多孔液体（PLs）作为一类具有永久孔隙的液体材料,兼具了液体吸收剂的易于管道输送、传质传热效果好等优点和固体吸附剂的高比表面积、高孔隙率等优点,有望成为新一代CO2捕集的绿色变革性介质。该文首先简单介绍了多孔液体发展脉络;然后,重点聚焦于多孔液体在CO2的吸附/吸收、膜分离、催化转化等领域的应用展开探讨,并对多孔液体性能和优缺点进行分析归纳。最后,对多孔液体目前面临的挑战和未来发展趋势进行了展望。     

燃煤烟气中SO2对氨法脱碳的影响

利用湿壁塔实验台对燃煤烟气中SO₂对氨水溶液［1%～7%(质量）］吸收CO₂的影响进行了实验研究,具体分析了不同反应温度（20～80℃）和CO₂体积分数（5%～20%）条件下,CO₂传质通量及传质系数随SO₂浓度和SO₂负载量的变化规律。结果表明, SO₂浓度由0增至11428 mg·m^-3,CO₂传质通量及传质系数均有一半左右降幅,而SO₂负载量［0.1～0.4 mol SO₂·（mol NH₃）^-1］的增加,同样导致CO₂传质通量及传质系数明显减小。氨水浓度及反应温度增加可有效提高CO₂传质通量和传质系数,相对降低SO₂对CO₂传质的影响。CO₂浓度的增加可明显提高其传质通量,但是CO₂的传质系数有所降低。