燃煤电厂烟气MDEA/PZ混合胺法碳捕集工艺模拟分析

采用混合胺吸收剂替代传统一乙醇胺（MEA）吸收剂是降低有机胺法碳捕集工艺能耗的重要方法。利用Aspen plus软件模拟了以甲基二乙醇胺(MDEA)/哌嗪(PZ)混合胺为吸收剂的燃煤电厂每年百万吨CO₂捕集工艺系统，考察了贫液负荷、MDEA/PZ混合胺浓度、MDEA/PZ比例和解吸压力等因素对解吸塔再沸器热负荷和冷凝器冷负荷的影响。通过对这些影响因素下吸收塔内液相温度分布和CO₂负荷分布变化揭示了MDEA/PZ对CO₂的吸收特性。此外，进一步分析了不同影响因素下解吸塔内气液相CO₂浓度驱动力和气液相级间温度驱动力分布特性，发现了强浓度驱动力和低温度驱动力分布更有利于降低再生能耗。研究表明，由30%MDEA和20%PZ组成的混合胺液在贫液负荷为0.08和解吸压力为2.02×10⁵Pa时，再沸器热负荷和塔顶冷凝负荷分别为2.76GJ/tCO₂和0.60GJ/tCO₂，相比传统MEA吸收剂降低了20.92%和40.0%。     

Modelling of an IGCC plant with carbon capture for 2020

Currently several industrial scale IGCC - carbon capture demonstration plants are being planned. Thermodynamic simulations are a useful tool to investigate the optimal plant configuration. In order to demonstrate the potential of the next generation of IGCC with CCS a thermodynamic model was developed using conventional but improved technology. The plant concept was verified and simulated for a generic hard coal and lignite. The simulation showed a net efficiency (LHV) of 38.5% and 41.9% for hard coal and lignite, respectively.The results are consistent with current studies but also indicate that major simulations were too optimistic. The auxiliary demand of an IGCC plant with carbon capture can be expected with 21 to 24% based on gross output. The drop in efficiency compared to the none-capture case is estimated with roughly 11 to 12%-points. During a sensitivity study the impact of process changes on plant efficiency and economics is evaluated. Releasing the captured CO₂ without compression is found to be economically favourable at CO₂ prices below 15 €/t and electricity prices above 100 €/MWh. Further the impact of carbon capture rate is quantified and an efficiency potential is indicated for lower CO₂ quality.     

煤制天然气工厂二氧化碳捕获技术

减少CO2的排放是国际社会当今迫切需要解决的问题,煤制天然气工厂在生产运行时会有大量的CO2排放,本文根据电厂CO2捕集技术,对适合煤制天然气工厂CO2捕集技术进行了分析。     

Modeling,optimization, and cost analysis of an IGCC plant with a membrane reactor for carbon capture

This article presents a theoretical study on the integration of a membrane reactor (MR) for carbon capture into an integrated gasification combined cycle (IGCC) plant. First‐principles, simplified systems‐level models for the individual IGCC units and the MR are introduced for their subsequent plantwide integration. The integrated plant model is then used for simulation studies that assume different MR characteristics. Using this model, an optimization problem is formulated to analyze the MR effects when adding it to the IGCC plant, while satisfying all of the process constraints in streams and performance variables. The solution of this optimization problem indicates improvements in the original case studies, including capital cost savings as high as $18 million for the optimal case under nominal process conditions. To determine the cost implications of inserting the MR into the IGCC plant, a differential cost analysis is performed taking into account major plant capital and operating costs. This analysis considers the same amount of coal and power generation for cases with and without the MR. The results of this analysis based on a present value of annuity calculation show break even costs for the MR within the feasible range for membrane fabrication, even for short membrane lifetimes. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1568–1580, 2016     

Equilibrium and kinetics analysis of carbon dioxide capture using immobilized amine on a mesoporous silica

Thermogravimetric analysis is used to study the adsorption kinetics, equilibrium, and thermodynamics of CO₂ on immobilized polyethylenimine sorbent impregnated on a mesoporous silica over the range of 300–390 K and 5–100% CO₂ concentration. Adsorption isotherm models were fitted to the experimental data indicating that a change in adsorption mechanism occurred near 70^°C. Below this temperature, the adsorption data followed the heterogeneous isotherms, while data taken at higher‐temperatures followed isotherms for homogeneous surfaces. Heat of sorption was estimated to be 130 kJ/mole for the low‐temperature regime, but this decreased to 48 kJ/mole above 70^°C. The rate of CO₂ fractional uptake decreased as temperature increased. A phenomenological kinetic model was derived from the Weibull distribution function using a nucleation growth theory to describe the two‐step process. The kinetic model was used to predict the uptake at different operating conditions and resulted in good agreement with experimental data. Published 2012 American Institute of Chemical Engineers AIChE J, 2013     

A controllability analysis of a pilot‐scale CO2 capture plant using ionic liquids

Nowadays there is a world concern on the impact and effect of large CO₂ atmospheric concentrations on human health. Fossil‐fuel combustion processes in power plants are among the major contributors to this issue. Hence, it becomes important to develop new clean and sustainable processes aimed to reduce the amount of CO₂ released to atmosphere by combustion processes in power plants. One of the best feasible manners to achieve this purposes lies in the use of a closed‐loop control system able to keep the amount of green‐house gases under specification even in the presence of unexpected scenarios. Of course, CO₂ capture has been extensively researched in the past. However, in this regard the industrial practice has consisted in using Amines leading to sustainability and safety issues. Hence, it makes sense to seek for new and potentially environmental friendly process design to address CO₂ reduction from power plants but applying a new type of sustainable stripping solvents. In this work we address the sustainable CO₂ reduction issue from a process control point of view applying a previous design proposed by our research team based on the deployment of Ionic Liquids (IL) as potential green solvents and developing an efficient and decentralized multiloop control system. We demonstrate that the closed‐loop system is able to maintain the CO₂ concentration levels under specification by testing in presence of several demanding scenarios. Overall, from an economic, sustainable and control point of view it looks feasible to replace the traditional amines‐based CO₂ capture process by other alternatives based on the application of IL as potential green solvents. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3298–3309, 2016     

Dynamic mechanical properties of keratin fibers during water absorption and desorption

The dynamic modulus and loss angle of keratin fibers have been measured during changes of relative humidity at a fixed fiber strain, temperature, and frequency of oscillation. From these measurements and the observation of an overshoot in loss angle in particular, certain conclusions about the structure of fibers can be made. This overshoot during absorption can be attributed to an interaction between two phases of keratin fibers. When a fiber at a fixed strain is dried from the wet state, the amount of α helices that have opened up during extension in water remains practically constant. A fiber that has been extended in the dry state contains α helices which open more rapidly than in the wet state for a given strain and rate of strain. When a wet fiber is dried and then rewetted while it is held at a fixed strain, the fiber achieves essentially the same structural state as in its original strained state.     

Chemical absorption and desorption of carbon dioxide from hot carbonate solutions

Absorption and desorption rate data for the system CO₂-hot carbonate solutions are presented. The data are interpreted on the basis of a film-theory model developed following the procedure recently presented by Astarita and Savage [1]. The agreement is very satisfactory. Values of the kinetic constant of the rate-determining step, previously known only up to a temperature of 40°C, have been obtained up to 110°C.     

Growth rate of carbon filaments during methane pyrolysis on an iron catalyst with analysis using a kinetic-thermodynamic approach

Optical microscopy has been used to determine the Arrhenius parameters of the linear growth rate for nano- and microfilaments of about ∼100 nm and larger in diameter. The quasi-steady state linear growth rates of carbon filaments in methane/hydrogen pyrolysis on an iron catalyst have been measured for filaments grown in a gas flow reactor at temperatures of 950-1050 °C. The filament growth rate as a function of the carbon activity of the feedstock CH₄/H₂ mixtures was shown to have both a local maximum at the carbon activities of about 200-300 and a local minimum at higher carbon activities, followed by another sharp increase at richer methane mixtures. The magnitude of the maximum was determined by the contribution of gas phase pyrolysis products to filament growth. A sharp increase in the growth rate after its local minimum was explained by changes in the growth mechanism mode, which, in turn, might be caused by melting of a catalyst particle. To analyze the kinetic data, a combined kinetic-thermodynamic approach was used.     

化学吸收法CO2捕集解吸能耗的分析计算

推导出了化学吸收法CO2捕集工艺解吸总能耗的准确计算公式,根据年产量100万吨CO2的捕集工艺流程的节点参数,分析计算了解吸能耗中各项能耗的大小,并与Leites、晏水平、王海波等能耗估算公式结果进行了对比。分析表明,本文推导的能耗计算公式适用于设计后或运行时的能耗计算,在捕集工艺设计前可采用Leites、晏水平、王海波等公式估算解吸能耗。其中晏水平公式考虑了循环倍率,因此能耗估算公式的适用性强,循环倍率和比热容取值偏差不大时,估算精度较高。通过对推导出的解吸能耗公式的分析,即使吸收剂质量浓度、溶液的再生度、贫富液换热器的性能一定,仍能进一步降低解吸总能耗,并提出了进一步降低解吸总能耗的有效措施。     

CO2 capture using some fly ash-derived carbon materials

Adsorption is considered to be one of the more promising technologies for capturing CO₂ from flue gases. For post-combustion capture, the success of such an approach is however dependent on the development of an adsorbent that can operate competitively at relatively high temperatures. In this work, low cost carbon materials derived from fly ash, are presented as effective CO₂ sorbents through impregnation these with organic bases, for example, polyethylenimine aided by polyethylene glycol. The results show that for samples derived from a fly ash carbon concentrate, the CO₂ adsorption capacities were relatively high (up to 4.5 wt%) especially at high temperatures (75 °C), where commercial active carbons relying on physi-sorption have low capacities. The addition of PEG improves the adsorption capacity and reduces the time taken for the sample to reach the equilibrium. No CO₂ seems to remain after desorption, suggesting that the process is fully reversible.     

基于碳捕集的燃煤机组热力系统优化及技术经济分析

碳捕集和封存是实现电力低碳化发展的关键所在,以600 MW机组为例,研究了碳捕集系统的能量流和质量流。提出了碳捕集系统与燃煤机组的耦合方式,计算了参考电站和碳捕集电站的热经济性。建立了碳捕集电站优化模型,以粒子群算法作为优化模型的求解算法,获得了系统的最优解。基于各设备投资成本,建立了碳捕集电站发电成本和CO2减排成本模型,研究了碳捕集电站的技术经济性。利用系统灵敏度分析方法,研究了碳税收和碳售价对发电成本和CO2减排成本的影响。结果表明：优化后碳捕集电站的热效率比优化前提高了1.1%;当CO2税收额高于0.33元/(kgCO2)时,碳捕集电站的经济性优于参考电站。     

Dynamic modelling of the absorber of a post-combustion CO2 capture plant: Modelling and simulations

Modelling work related to carbon dioxide (CO₂) capture technologies is of great importance with respect to the design, control, and optimization of the capture process. Development of dynamic models as such is important since there is much information embedded with the dynamics of a plant which cannot be studied with steady state models. A model for the absorption column of a post-combustion CO₂ capture plant is developed following the rate based approach to represent heat and mass transfer. The Kent–Eisenberg model is used to compute the transfer and generation rates of the species. Sensitivity of the model for different physiochemical property correlations is analyzed. The predictions of the dynamic model for the capture plant start-up scenario and operation of the absorption column under varying operating conditions in the up-stream power plant and the down-stream stripping column are presented. Predictions of the transient behaviour of the developed absorber model appear realistic and comply with standard steady state models.     

Pilot plant study of two new solvents for post combustion carbon dioxide capture by reactive absorption and comparison to monoethanolamine

Application of new solvents will substantially contribute to the reduction of the energy demand for the post combustion capture of CO₂ from power plant flue gases. The present work describes tests of such new solvents in a gas-fired pilot plant, which comprises the complete absorption/desorption process (column diameters 0.125 m, absorber/desorber packing height 4.25/2.55 m, packing type: Sulzer BX 500, flue gas flow 30–100 kg/h, CO₂ partial pressure 35–135 mbar). Two new solvents CESAR1 (0.28 g/g 2-amino-2-methyl-1-propanol+0.17 g/g piperazine+0.55 g/g H₂O) and CESAR2 (0.32 g/g 1, 2-ethanediamine+0.68 g/g H₂O), which were developed in an EU-project, were systematically studied and compared to MEA (0.3 g/g monoethanolamine+0.7 g/g H₂O). The two new solvents and MEA were studied in the same way in the pilot plant and detailed results are reported for all solvents. In the present study the structured packing Sulzer BX 500 is used. The measurements are carried out at a constant CO₂ removal rate of 90% by an adjustment of the regeneration energy in the desorber for systematically varied solvent flow rates. An optimal solvent flow rate leading to a minimum energy requirement is found from these studies. Direct comparisons of such results can be misleading if there are differences in the kinetics of the different solvent systems. The influence of kinetic effects is experimentally studied by varying the flue gas flow rate at a constant ratio of solvent mass flow to flue gas mass flow and constant CO₂ removal rate. Results from these studies indicate similar kinetics for CESAR1, CESAR2 and MEA. The direct comparison of the pilot plant results for these solvents is therefore justified. Both CESAR1 and CESAR2 show improvements compared to MEA. The most promising is CESAR1 with a reduction of about 20% in the regeneration energy and 45% in the solvent flow rate.     

电厂和碳捕集装置同步集成与调度优化研究

由于全球碳排放量持续增加所引发的环境问题日益严重,发展低碳技术迫在眉睫。在化石燃料发电厂的尾端加入碳捕集装置能够有效减少燃煤电厂的碳足迹,达成减排指标。然而,碳捕集装置的高设备成本以及运行所附带的效率惩罚和经济惩罚阻碍了其与电厂装置的集成与部署。为了在满足碳减排量的同时有效提高电厂和碳捕集装置的总体效益,建立了一个基于数学规划的系统优化设计与调度方法,将发电厂与一个增加烟气旁路和溶剂储罐的碳捕集装置进行集成,并在电厂蒸汽动力循环部分引入分级透平,旨在考虑电价波动的情况下,充分利用碳捕集装置的操作灵活性与蒸汽透平分级做功的优势,对集成系统进行调度优化。最后,通过算例验证了模型的可靠性与有效性,分析归纳了电厂与碳捕集装置协同调度的主要特性与规律。     

Dynamic modelling of CO2 absorption for post combustion capture in coal-fired power plants

Power generation from fossil fuel-fired power plants is the largest single source of CO₂ emissions. Post combustion capture via chemical absorption is viewed as the most mature CO₂ capture technique. This paper presents a study of the post combustion CO₂ capture with monoethanolamine (MEA) based on dynamic modelling of the process. The aims of the project were to compare two different approaches (the equilibrium-based approach versus the rate-based approach) in modelling the absorber dynamically and to understand the dynamic behaviour of the absorber during part load operation and with disturbances from the stripper. A powerful modelling and simulation tool gPROMS was chosen to implement the proposed work. The study indicates that the rate-based model gives a better prediction of the chemical absorption process than the equilibrium-based model. The dynamic simulation of the absorber indicates normal absorber column operation could be maintained during part load operation by maintaining the ratio of the flow rates of the lean solvent and flue gas to the absorber. Disturbances in the CO₂ loading of the lean solvent to the absorber significantly affect absorber performance. Further work will extend the dynamic modelling to the stripper for whole plant analysis.     

Modelling reactive absorption of CO2 in packed columns for post-combustion carbon capture applications

A rate-based process model for the reactive absorption of carbon dioxide (CO₂) from a gas mixture into an aqueous monoethanolamine (MEA) solution in a packed column is developed. The model is based on the fast second-order kinetics for the CO₂-MEA reactions and takes into account the mass transfer resistances. The heat effects associated with the absorption and chemical reaction are included through energy balances in the gas and liquid phases. Appropriate correlations for the key thermodynamic and transport properties and for the gas-liquid mass transfer are incorporated into the model to ensure reliable predictions. The model predictions are validated by simulating a series of experiments conducted in pilot and industrial scale absorption columns with random and structured packings reported in the literature. Comparisons between the simulation results and the experimental data reveal good quality predictions of the gas phase CO₂ and MEA concentrations and the liquid temperature along the column height. The sensitivity studies reveal that the correlations for the gas- and liquid-film mass transfer coefficients given by Onda et al. (1968) provide better predictions than the penetration theory of Higbie (1935) and the correlation of Bravo et al. (1985).     

Adsorption and desorption of halogenated hydrocarbons using activated carbon

Environmental hazards caused by halogenated hydrocarbons and increasingly stringent regulations for limiting their emission require comprehensive investigations of these substances. The present work deals with the adsorption and desorption of halogenated hydrocarbons on activated carbon. The results could be useful in the utilization of landfill gases because halogenated hydrocarbons must be removed in order to avoid pollution and the loaded activated carbons have to be regenerated. Activated carbons are well suited to removal and recovery of halogenated hydrocarbons from gas flows.     

Design of packed towers for absorption and desorption of carbon dioxide using hot promoted K2CO3 solution

The mathematical model developed for the design of a packed column for the absorption of carbon dioxide in hot promoted potassium carbonate solution (Gas Sep Purif (1989) Vol 3 p 152; (1990) Vol 4 p 58) is extended to take into account the condensation of water present in the gas feed to the absorption column. The revised model is further extended to obtain the design of the desorption column where the feed gas is pure steam and the exit gas consists of carbon dioxide and steam. The integration of the relevant differential equations for the desorption tower is done by starting the calculations from the top conditions of the column where the exit flow rate of steam and exit gas temperature are guessed and verified later after completing the tower calculations with the help of the overall material and energy balance calculations.     

杂质对MDEA-TETA溶液吸收与解吸CO2性能的影响

本文实验研究了MDEA-TETA溶液中可能存在的杂质对其吸收与解吸CO2性能的影响,这些杂质包括固体颗粒FeS、SiO2、活性炭;无机盐FeSO4、NaCl、CaCl2、MgCl2;有机物甲醇、三甲胺、三乙醇胺、二甲基乙醇胺等.研究结果表明:FeSO4、三甲胺、三乙醇胺可促进MDEA-TETA溶液对CO2的吸收;其它杂...