Heterogeneous Vapor Condensation Research Articles

Promoting fine particle removal in cyclone by spray agglomeration and heterogeneous condensation

By adding a spray chamber in front of the cyclone separator, spray agglomeration and heterogeneous vapor condensation were combined to improve the removal effect of the cyclone separator on fine particles, which is used for the deep treatment of high-humidity industrial flue gas and fine particles. Fine particles can form agglomerates through the capture effect of micron droplets, and can also grow in size through heterogeneous vapor condensation in supersaturated water vapor environment, thus being effectively removed by cyclone separators. Supersaturated water vapor environment was a necessary condition for heterogeneous vapor condensation. Numerical simulation results showed that supersaturated water vapor environment can be formed in the spray chamber when the relative humidity of the original flue gas was high, and the higher the relative humidity, the higher the supersaturation and the larger the supersaturation area. The experimental results indicated that spray agglomeration and spray coupling heterogeneous condensation increased the particle removal efficiency of the cyclone separator by 11.6 % and 22.6 %, and the removal efficiency in the 2–4 μm “fish-hook” range was increased by 21.6 % and 41.7 %, respectively. This technology was successfully applied for the first time in the deep treatment of the tail gas in Fluid Catalytic Cracking (FCC) catalyst production industry, which can ensure that the particle emission concentration was within 20 mg/Nm3.

Emission reduction of condensable particulate matter in ammonia-based desulfurized flue gas by heterogeneous vapor condensation

With ultra-low emissions being implemented in China, the proportion of condensable particulate matter (CPM) increased gradually in total particulate matter (TPM). To reduce the CPM emission, a novel method based on heterogeneous vapor condensation via heat exchanger was proposed. The phase of gaseous CPM would be changed to solid or liquid phase by temperature drop of desulfurized flue gas and then the particle CPM might be enlarged by heterogeneous vapor condensation. With the effect of inertia force, thermophoretic force, and diffusiophoresis force, the enlarged CPM particles would be captured by liquid film, which was formed on the surface of fluoroplastic capillaries. The experimental results indicated that reduction rate for filterable particulate matter (FPM) and CPM would be 26.67% and 30.84% by heterogeneous vapor condensation under typical conditions, and the SO42− and NH4+ were main ions in water-soluble ions for FPM/CPM. The influences of temperature drop and original temperature of desulfurized flue gas were also investigated. The higher temperature drop of desulfurized flue gas was beneficial for reduction of CPM emission and the effect of original desulfurized flue gas temperature was limited for CPM emission reduction. The results also manifested that the optimum temperature drop is 4–6 °C for different desulfurized flue gas temperatures.

Promoting fine particle removal in double-tower cascade wet flue gas desulfurization system by flue gas temperature reduction

The emission of fine particles from coal-fired power plants could cause many environmental issues. To promote the fine particle removal in coal-fired flue gas, a process involving a double-tower cascade wet flue gas desulfurization system based on heterogeneous water vapor condensation via flue gas temperature reduction between two desulfurization towers is proposed. In the established supersaturated water vapor environment, fine particles could develop into lager condensational-droplets, and then be efficiently removed in the subsequent secondary tower. The results of numerical analysis for this proposed process indicated that it was feasible under most scenarios, and the experimental results showed that the removal efficiency of fine particles in all size ranges could be promoted. Furthermore, the effects of some key operating parameters were also studied, and the results indicated that the total removal efficiency would be promoted by 15–20% and the fine particle emission could be reduced by 30–40% in most cases.

Promoting the Removal of Particulate Matter by Heterogeneous Vapor Condensation in a Double-Loop Wet Flue Gas Desulfurization System

According to the theory of heterogeneous vapor condensation, an innovative process to promote particulate matter removal in a double-loop wet flue gas desulfurization system was proposed. The essen...

Improving the removal of fine particulate matter based on heterogeneous condensation in desulfurized flue gas

To reduce the emission of fine particulate matter (PM) in coal-fired power plants, a new method aimed to improve the removal of fine particulate matter based on heterogeneous vapor condensation was investigated. The ideal supersaturation environment, necessary to the occurrence of heterogeneous vapor condensation, was achieved by reducing the initial temperature of limestone-gypsum desulfurization flue gas with a fluorine plastic heat exchanger. The temperature drop, initial relative humidity and initial temperature of desulfurized flue gas have an important influence on the establishment of ideal supersaturation environment and the reduction efficiency of fine particulate matter. Numerical calculation indicates that a higher temperature drop and initial relative humidity of the desulfurized flue gas is beneficial to the establishment of ideal supersaturation environment, while the influence of initial temperature of desulfurized flue gas is unobvious. It has been also experimentally proved that the increase of temperature drop and initial relative humidity have a positive effect to the improvement of the reduction efficiency. However, it can be also found that the reduction efficiency changes slightly with the variation of the initial temperature of desulfurized flue gas. Therefore, this method is suitable for different initial temperatures of desulfurized flue gas and is more applicable for practical industrial applications. Most commonly, the optimal value of temperature drop of desulfurized flue gas is in the range of 4 to 6 °C and the corresponding number concentration of fine particulate matter emission can be reduced as high as about 43%.

Reducing fine particle emissions by heterogeneous vapor condensation after wet desulfurization process

AbstractBACKGROUNDThe fine particles emitted from coal‐fired power plants has caused many health and environmental problems. Reducing the fine particle emissions from coal‐fired power plants is of great significance. In this work, a novel process of heterogeneous vapor condensation after wet desulfurization was investigated to reduce the emission of fine particles.RESULTSThe proposed novel process was realized via three different methods, and numerical calculation indicated that it was feasible. The experimental results showed that the temperature drop of desulfurized flue gas due to the added steam and cold air had a positive effect on the improvement in reduction of fine particles. The experimental results also showed that the heat exchange method was applicable to desulfurized flue gas at different temperatures. However, the steam addition method was more suitable for original desulfurized flue gas at lower temperatures while the cold air addition method has more advantages in the case of original desulfurized flue gas at higher temperatures.CONCLUSIONThe novel process proposed in this paper was feasible for industrial application. Under typical conditions, the fine particle emissions in the final discharged flue gas were reduced by 30–40% using this process. © 2017 Society of Chemical Industry

Removal of sulfuric acid aerosols in desulfurized flue gas by adding moist air

BACKGROUND The reduction of sulfuric acid aerosol emissions in coal fired power plant is of great importance. Based on the classical theory of heterogeneous vapor condensation, a novel engineering process was proposed to increase the efficiency of removal of sulfuric acid aerosols by adding moist air in the condensational growth chamber (CGC), following the desulfurization scrubber. RESULTS The theoretical analysis showed that this novel process was feasible. The experimental results indicated that the efficiency of removal of sulfuric acid aerosols was mainly influenced by the amount of moist air added and the humiture of desulfurized flue gas and moist air. Higher humiture of desulfurized flue gas could promote removal efficiency, whereas higher temperature of moist air was unfavorable. However, the influence of the relative humidity of moist air was not obvious. Moreover, increasing the mixture ratio was also beneficial for the improvement of removal performance in the range below 10:20. CONCLUSION The process proposed was feasible for industrial application. The efficiency of removal of sulfuric acid aerosols was enhanced to 30–50% by this novel process. © 2016 Society of Chemical Industry

Kinetic modeling of the formation and growth of inorganic nano-particles during pulverized coal char combustion in O2/N2 and O2/CO2 atmospheres

In the formation of nano-particles during coal char combustion, the vaporization of inorganic components in char and the subsequent homogeneous particle nucleation, heterogeneous condensation, coagulation, and coalescence play decisive roles. However, conventional measurements cannot provide detailed information on the dynamics of nano-particle formation and evolution. In this work, a sophisticated intrinsic char kinetics model that considers ash effects (including ash film formation, ash dilution, and ash vaporization acting in tandem), both oxidation and gasification by CO2 and H2O, homogeneous particle nucleation, heterogeneous vapor condensation, coagulation, and coalescence mechanisms is developed and used to compare the temporal evolution of the number and size of nano-particles during coal char particle combustion as a function of char particle size, ash content, and oxygen content in O2/N2 and O2/CO2 atmospheres. Based on comparisons with measurements of char particle temperature, carbon conversion, mineral vaporization, and mean size of nano-particles at various residence times, the model can accurately predict the transient combustion of pulverized coal char particles and nano-particle formation and growth. Model results show that in either O2/N2 or O2/CO2 atmospheres, the char combustion temperature has a dominant effect on the formation and growth of nano-particles. High char burning temperatures result in a high mineral vaporization rate within the char particle, and subsequent high nucleation and condensation rate, and consequently more and larger nano-particles. As a result, high oxygen content, low ash content, and small sized char particles, all of which promotes high local char burning temperatures, yield more nano-particles and shift the nano-particle size distribution to larger sizes. In comparison to combustion in O2/N2, both the number density and size of the nano-particles formed in O2/CO2 are lower. Unlike condensation, which contributes to particle growth until the vapor molecules are fully consumed, nucleation ceases during the last stage of char combustion.

The abatement of fine particles from desulfurized flue gas by heterogeneous vapor condensation coupling two impinging streams

A novel process was proposed for fine particles abatement via heterogeneous vapor condensation coupling two impinging steams (TIS) technique in this paper. The essential supersaturation was established by adding steam or humid air into desulfurized flue gas, and the application of TIS technique in this process made the mixture of desulfurized flue gas and humid air or steam more sufficient. The fine particles were enlarged by the heterogeneous vapor condensation and the collision-coalescence in two impinging steams condensational growth chamber (TISCGC), then the enlarged fine particles were intercepted by a wire mesh demister at the top of TISCGC. The results indicated that the enlargement of fine particles in TISCGC was more significant than that of conventional condensational growth chamber (CCGC), thus the fine particle removal performance of wire mesh demister was better. The removal performance of fine particles by this process was influenced by many factors, such as flue gas velocity of opposing jets in TISCGC, additive amount of steam or humid air and the desulfurized flue gas temperature. Under the optimum conditions, the removal efficiency of TISCGC could be increased to 50–60% by using this process.

Abatement of Fine Particle Emission by Heterogeneous Vapor Condensation During Wet Limestone-Gypsum Flue Gas Desulfurization

The fine particles in desulfurized flue gas comprise coal-fired fine particles from combustion and generated fine particles from desulfurization. The abatement of fine particle emission by heterogeneous vapor condensation during wet flue gas desulfurization (WFGD) is experimentally investigated in this paper. A supersaturation atmosphere, which is necessary for heterogeneous vapor condensation, is established by increasing the humidity and reducing the temperature of the flue gas before WFGD. The improvement of the removal of coal-fired fine particles and the inhibition of generated fine particles formation in desulfurization process by heterogeneous vapor condensation were studied, and the influences of inlet flue gas parameters on the emission of total fine particles, including coal-fired fine particles and generated fine particles during desulfurization, are examined. The results indicate that the total emission of fine particles in desulfurized flue gas can be significantly decreased via heterogeneous...

Improving the removal efficiency of sulfuric acid droplets from flue gas using heterogeneous vapor condensation in a limestone‐gypsum desulfurization process

ABSTRACTBACKGROUNDEmissions of sulfuric acid droplets have caused many problems. Improving the removal efficiency of sulfuric acid droplets is of great importance. A novel process based on heterogeneous vapor condensation was proposed in this paper to improve the removal efficiency of sulfuric acid droplets in a limestone–gypsum desulfurization process.RESULTSThe results indicated that the sulfuric acid droplets were relatively easily activated in a supersaturated vapor environment and condensed into larger droplets. The removal efficiency of sulfuric acid droplets in a wet flue gas desulfurization (WFGD) system could be significantly improved. The improvements were mainly related to the inlet flue gas moisture content and temperature. A relatively higher moisture content and lower temperature of inlet flue gas improved the removal performance. Moreover, the liquid‐to‐gas ratio and the SO3 concentration also contributed to the improvement in removal efficiency. However, a higher temperature of the desulfurization slurry was unfavorable.CONCLUSIONThe novel process based on heterogeneous vapor condensation is suitable for industrial application. The removal efficiency of sulfuric acid droplets can be improved from 30 ∼ 40% to greater than 60%. © 2016 Society of Chemical Industry

Droplet growth and coarsening during heterogeneous vapor condensation.

A theoretical description of droplet growth and coarsening is presented for vapor condensing onto a partially wetting surface. Both individual droplet growth and coalescences are included in the description. The coupling of these growth mechanisms results in two characteristic lengths. The radii of individual droplets, nucleated onto the surface, increase as a power of time: R\ensuremath{\sim}${t}^{m}$. Diffusion-limited growth on the surface leads to a characteristic exponent m=(1/4. As a result of coalescences, however, the average droplet radius grows with an exponent of 3m. Further predictions of the theory are also discussed.

Point Imperfections and Epitaxy of Some fcc Metals

It has been found that plane, line, and point imperfections play an important role in the incidence, alignment, and morphology characteristic of metal nuclei formed by heterogeneous condensations of heterogeneous vapor condensation involving relatively strong homogeneous interactions and weak heterogeneous interactions can now be applied to the mechanism of metal film formation with some confidence for specific metalsubstrate condensation systems. The high sensitivity of film orientation and structure to the initial stages of nucleation for these systems suggests that critical factors pertaining to the defect structure of the substrate and to the specific vacuum conditions prior to and during condensation influence film formation. For example, the low epitaxial temperature observed on irradiated surfaces indicates that epitaxial alignment of nuclei on ordered, tight-binding sites is critical in inducing epitaxy at low temperature. Some of the significant factors essential to the influence of these variabl...