膜吸收法烟气脱碳研究进展

介绍了采用膜吸收法进行烟气脱碳过程中膜材料的种类、吸收液的选择以及膜吸收的耦合对脱碳的影响。综述了工艺流程、工艺参数及传质模型对膜吸收过程的影响,指出了膜吸收法烟气脱碳工程应用的经济性及发展方向。     

Spirulina platensis Culture with Flue Gas Feeding as a Cyanobacteria‐Based Carbon Sequestration Option

The scientific community is currently examining potential approaches in order to reduce the anthropical contributions to global warming. One approach is carbon capture and its storage, i.e., capturing CO₂ at its source and storing it indefinitely to avoid its release into the atmosphere. Conversion of CO₂ by microalgae or cyanobacteria is a sequestration option. Here, the application of an air‐lift reactor to flue gas treatment using cyanobacteria for the absorption of CO₂ was investigated, with the simultaneous abatement of NO_x. A Spirulina platensis culture was fed with CO₂ and NO_x, simulating a flue gas. The preliminary test yielded positive indications on the process feasibility, both in terms of cell productivity (86.8 mg L^–1d^–1) and CO₂ abatement (229 mg d^–1). Opportune dosages of flue gas used in fed‐batch test achieved a high abatement of CO₂ (407 mg d^–1), 90.0 % removal of NO_x, and a biomass production of 188.7 mg L^–1d^–1.     

Prediction of the Removal Efficiency of a Novel Two‐Stage Hybrid Scrubber for Flue Gas Desulfurization

Emission of SO₂ from various industrial sources occurs in varying concentrations and quantities. The operation of scrubbers as SO₂ control devices is getting more and more attention as pollution control regulations are tightened. Experimental investigations on the scrubbing of SO₂ in a novel two‐stage hybrid (spray‐cum‐bubble column) scrubber using water and dilute sodium alkali are reported. Empirical and semi‐empirical correlations are developed for the prediction of the performances of the bubble and the spray sections in terms of various pertinent variables of the system for water and alkaline scrubbing, respectively. The contribution of the mass transfer enhancement factor towards the removal of SO₂ has been exploited while developing the semi‐empirical correlation for the prediction of performance in alkaline scrubbing. The predicted values are in excellent agreement with the experimental values. Finally, the operating features of the scrubber and design aspects are discussed in order to develop our understanding for practical applications.     

Ionic liquids for CO2 capture—Development and progress

Innovative off-the-shelf CO₂ capture approaches are burgeoning in the literature, among which, ionic liquids seem to have been omitted in the recent Intergovernmental Panel on Climate Change (IPCC) survey. Ionic liquids (ILs), because of their tunable properties, wide liquid range, reasonable thermal stability, and negligible vapor pressure, are emerging as promising candidates rivaling with conventional amine scrubbing. Due to substantial solubility, room-temperature ionic liquids (RTILs) are quite useful for CO₂ separation from flue gases. Their absorption capacity can be greatly enhanced by functionalization with an amine moiety but with concurrent increase in viscosity making process handling difficult. However this downside can be overcome by making use of supported ionic-liquid membranes (SILMs), especially where high pressures and temperatures are involved. Moreover, due to negligible loss of ionic liquids during recycling, these technologies will also decrease the CO₂ capture cost to a reasonable extent when employed on industrial scale. There is also need to look deeply into the noxious behavior of these unique species. Nevertheless, the flexibility in synthetic structure of ionic liquids may make them opportunistic in CO₂ capture scenarios.     

Pilot plant study of post-combustion carbon dioxide capture by reactive absorption: Methodology, comparison of different structured packings, and comprehensive results for monoethanolamine

Post-combustion carbon capture (PCC) from fossil fuel power plants by reactive absorption can substantially contribute to reduce emissions of the greenhouse gas CO₂. To test new solvents for this purpose small pilot plants are used. The present paper describes results of comprehensive studies of the standard PCC solvent MEA (0.3 g/g monoethanolamine in water) in a pilot plant in which the closed cycle of absorption/desorption process is continuously operated (column diameters: 0.125 m, absorber/desorber packing height: 4.25/2.55 m, packing type: Sulzer BX 500, flue gas flow: 30-110 kg/h, CO₂ partial pressure: 35-135 mbar). The data establish a base line for comparisons with new solvents tested in the pilot plant and can be used for a validation of models of the PCC process with MEA. The ratio of the solvent to the flue gas mass flow is systematically varied at constant CO₂ removal rate, and CO₂ partial pressure in the flue gas. Optimal operating points are determined. In the present study the structured packing Sulzer BX 500 is used. The experiments with the removal rate variation are carried out so that the results can directly be compared to those from a previous study in the same plant that was carried out using Sulzer Mellapak 250.Y. A strategy for identifying the influence of absorption kinetics on the results is proposed, which is based on a variation of the gas load at a constant L/G ratio and provides valuable insight on the transferability of pilot plant results.     

冶炼烟气中SO2催化还原为元素S的研究进展

冶炼烟气中SO2催化还原为元素S是利用适当的还原剂将烟道气中的SO2选择性地催化还原成单质硫,这种方法的最终产物是固态单质硫,无废水废渣排放。因此,把烟气中的SO2选择性的还原为单质硫将是一种既具有经济效益又具有社会效益的适合我国国情的烟气脱硫方法。本文综述了目前将烟气中SO2催化还原为元素硫进行回收的主要方法,分析了每种方法的优缺点,并提出烟气中SO2直接还原脱硫技术所存在的问题和发展趋势。     

烟气脱硫技术的研究

概述了国内外烟气脱硫技术的应用现状、脱硫原理及其特点,并提出了我国烟气脱硫技术的研究开发方向。     

Interfacial area and mass transfer in carbon dioxide absorption in TEA aqueous solutions in a bubble column reactor

The hydrodynamic behaviour and mass transfer of carbon dioxide removal process by aqueous solutions of triethanolamine (TEA) are analysed. The experiments were made in a bubble column reactor (BCR) as gas–liquid contactor. The interfacial area and mass transfer coefficient were calculated by using a photographic method based on the bubble diameter determination. The influence of operation conditions, liquid phase nature and chemical reaction on the mass transfer coefficient and gas–liquid interfacial area has been also analysed.     

Dry SO2 Removal Process Using Calcium/Siliceous‐Based Sorbents: Deactivation Kinetics Based on Breakthrough Curves

The removal of sulfur dioxide (SO₂) from simulated flue gas was investigated in a laboratory‐scale stainless steel fixed‐bed reactor using sorbents prepared from various siliceous materials, i.e., coal fly ash (CFA), oil palm ash (OPA) and rice husk ash (RHA) mixed with lime (CaO) by means of the water hydration method. Experiments were carried out with a flue gas flow rate of 150 mL/min, reaction temperature of 100 °C, and SO₂ concentration of 1000 ppm. It was found that sorbents prepared from RHA have high BET surface areas and high SO₂ sorption capacities, based on breakthrough curve analysis. In addition, the SO₂ breakthrough curves were also described in terms of a simple first‐order deactivation model containing only two rate constants, one of which, k_s, describes the surface reaction rate constant while the other, k_d, describes the deactivation rate constant. The values of k_s and k_d obtained from the deactivation kinetics model were in good agreement with the experimental breakthrough curves and were also compared with those available in the literature.     

Optimization of a Pilot‐Scale Amine Scrubber to Remove SO2: Higher Selectivity and Lower Solvent Consumption

A pilot‐scale study of flue gas desulfurization based on an amine‐based solvent using applicable industrial values was carried out for sulfur dioxide (SO₂) removal. The plant consisting of absorption and desorption columns was operated with different working parameters such as solvent flow rate, inlet concentration of SO₂, temperature of desorption column, and pH of absorption agent. The Taguchi method was utilized to obtain the best combination of working parameters for the most efficient reduction of SO₂ outlet concentration. The industrial gas‐to‐liquid ratio could be optimized by applying a defined SO₂ concentration, stripper temperature, and solvent pH value. The achieved efficiency is much better compared to our previous study while the gas‐to‐liquid ratio is higher in this work.     

Equilibria in a Limestone Based FGD Process: A Pure System and with Chloride Addition

On the basis of physical and chemical equilibria conditions a model of gaseous sulfur dioxide solubility in the solutions applied in an FGD (flue‐gas desulfurization) process was developed. The dependencies of solution pH in the bulk liquid and in the limestone particle vicinity on the calcium carbonate and/or on the dissolved sulfur dioxide content are presented. The influence of the concentration of dissolved carbon dioxide on pH, sulfite to sulfate oxidation conditions, limestone and calcium sulfite solubility are also discussed. The mechanisms leading to a decrease in calcium carbonate solubility or limestone particle blinding are explained. The restrictions in calcium chloride concentration for the reliable operation of an FGD process are predicted.     

木质素磺酸钠吸收烟道气中的SO2

本文就木质素磺酸钠溶液脱除烟道气中SO_2进行了实验研究。实验采用双搅拌气-液反应器,探讨了木质素磺酸钠的浓度、温度等因素对SO_2吸收的影响,并求取了化学吸收增强因子。结果表明,木质素磺酸钠能有效地脱除烟道气中的SO_2。     

Carbon Dioxide Absorption in Triethanolamine Aqueous Solutions: Hydrodynamics and Mass Transfer

The carbon dioxide absorption process by triethanolamine aqueous solutions was analyzed in a bubble‐column reactor taking into account the chemical reaction mechanism, gas‐liquid interfacial area, and mass transfer rate. A speciation study of this gas‐liquid system was developed by ¹H and ¹³C NMR spectroscopy in order to obtain the reaction mechanism and stoichiometry. The gas‐liquid interfacial area was evaluated considering the variations of bubble size distribution and gas holdup during the operation time. The liquid‐phase mass transfer coefficient was calculated from the carbon dioxide absorption rate data by interfacial area evolution and reaction stoichiometry.     

Recent developments on carbon capture and storage: An overview

The Intergovernmental Panel on Climate Change assumes the warming of the climate system, associating the increase of global average temperature to the observed increase of the anthropogenic greenhouse gas (GHG) concentrations in the atmosphere. Carbon dioxide (CO₂) is considered the most important GHG, due to the dependence of world economies on fossil fuels, since their combustion processes are the most important sources of this gas. CO₂ concentrations are increasing in the last decades mainly due to the increase of anthropogenic emissions. The processes involving CO₂ capture and storage is gaining attention on the scientific community as an alternative for decreasing CO₂ emission, reducing its concentration in ambient air. However, several technological, economical and environmental issues as well as safety problems remain to be solved, such as the following needs: increase of CO₂ capture efficiency, reduction of process costs, and verification of environmental sustainability of CO₂ storage. This paper aims to review the recent developments (from 2006 until now) on the carbon capture and storage (CCS) methodologies. Special attention was focused on the basic findings achieved in CCS operational projects.     

Multistablity, bistability and bubbles phenomena in a periodically forced ethanol fermentor

The numerical investigation results of the dynamic behavior of an ethanol fermentor excited by external sinusoidal periodic perturbations are reported. The characteristics of the discriminant of the cubic polynomial of the steady state autonomous model of the unforced fermentor were used to divide the parameter space into regions with different number of steady state solutions. The bioethanol fermentor exhibits interesting complicated dynamic behavior when the center of forcing is close to a static limit point (SLP) i.e. the discriminant=0. Numerical simulations have presented evidence for the existence of multistability, bistability and bubbles phenomena in the forced bioethanol fermentor. This is – to the best of our knowledge – the first study that shows these phenomena in the forced bioethanol fermentor. Multistablity is characterized by the coexistence of several attractors. It has been shown that, the multistability exhibits the coexistence of three attractors, two of them are chaotic and one quasi-periodic, and the bistability exhibits the coexistence of two attractors, one of them is periodic and the other is either periodic, quasi-periodic or chaotic attractor. In the multistabiliy region, we have observed that changing the forcing amplitude with the sequence of events there is an appearance of the bistability and then a transition to multistabilty. It has been shown that, the bubble region acts as a period doubling killer, which has a lethal effect in killing the universal period doubling scenario to chaos by reversing the sequence to period halving. It is also shown that, the unforced (14.55% increase in ethanol average concentration relative to the steady state operation) or forced (8.87% increase in ethanol average concentration relative to the steady state operation) unsteady state operations give better fermentor performance than the steady state operations with respect to the average ethanol concentration and yield. The investigation shows that the nature and the position of the center of forcing have significant effect on the dynamic response of the periodically forced fermentors. It has been found that, the forcing could be beneficial or harmful to the fermentor performance depending on the position of center of forcing. The system shows interesting phase planes at certain forcing amplitudes.     

HgCl2 sorption on lignite activated carbon: Analysis of fixed-bed results

Factors that influence kinetic reactivity and equilibrium between elemental mercury, carbon, and flue gas components have been the focus of numerous studies. This study pertains to recent bench-scale fixed-bed tests in which activated carbon was exposed to HgCl₂ in a flue gas composition typical of an unscrubbed eastern bituminous coal. Results are discussed in light of a refined binding site model based on the zigzag carbene structures recently proposed for electronic states at the edges of the carbon graphene layers.     

Chemical Changes of Canola Oil During Frying Under Atmospheric Condition and Combination of Nitrogen and Carbon Dioxide Gases in the Presence of Air

The effects of different frying methods; frying under atmospheric condition and frying in the presence of different ratios of nitrogen and carbon dioxide gases; were investigated on chemical changes of canola oil. The tests were conducted four times per day during four consecutive days. The chemical changes of oil samples were determined by analyzing peroxide value (PV), p-anisidine value (p-AV), totox value (TV) and acid value (AV). Irrespective of the test methods, PV increase was observed on the first day followed by significant (p < 0.05) reduction in the subsequent days. On the first day, the highest p-AV and TV was observed in oil fried under atmospheric condition and the lowest p-AV and TV for those fried under gases. However, from the second day, the p-AV and TV in frying under different ratios of nitrogen and carbon dioxide gases were significantly (p < 0.05) higher than the frying under atmospheric condition. Additionally, hydrolysis and oxidation of oil during frying resulted in continuous AV increase that among them atmospheric frying had the highest AV. In conclusion, atmospheric frying accelerates the rate of oil deterioration and application of nitrogen and carbon dioxide gases in the fryer could reduce the rate of oil disintegration.     

Shortcut Evaluation of Chemical Carbon Dioxide Utilization Processes

Chemical utilization of carbon dioxide seems to be an attractive option for the mitigation of greenhouse gas emissions. However, the respective processes themselves cause substantial greenhouse gas emissions. To achieve a good CO₂ balance, it is necessary not only to fix carbon but also to do this efficiently in terms of reactant supply and energy demand. An evaluation of the CO₂ balance requires detailed process simulation for the utilization reaction and the supply chain. To allow a quick evaluation of the potential to mitigate emissions, a number of estimation methods are presented.     

Effect of Carbon Dioxide Chemical Absorption on Bubble Diameter and Interfacial Area

The influence of a gas‐liquid chemical reaction on the interfacial area produced in a contactor is analyzed. Two different amines were used to capture carbon dioxide by chemical absorption. The effects of the operation time, the amine used, the concentration interval, and the gas flow rate on typical hydrodynamic parameters used in bubble columns such as the gas holdup and the Sauter mean diameter were investigated. These parameters were used to determine the interfacial area value. Significant influences on the gas‐liquid interfacial area were detected, mainly caused by the reaction rate intensity, the physicochemical properties of the liquid phase, and the gas flow rate fed to the contactor.