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 vapor condensation.
This decrease in the emission of coal-fired fine particles is mainly
related to the removal of fine particles via heterogeneous vapor condensation,
and the generation of fine particles from desulfurization is abated
because of both the decrease in the inlet flue gas temperature and
heterogeneous vapor condensation. Higher inlet flue gas humidity can
adequately reduce the emission of generated fine particles from desulfurization.
The reduction in the flue gas temperature before WFGD is the main
factor that inhibits the formation of fine particles and removes coal-fired
fine particles during desulfurization.
The
surface microstructure of the current collectors significantly
affects the electrochemical performance of lithium-ion batteries (LIBs).
This study shows that an effective method of orthogonal ploughing/extrusion
is to fabricate three-dimensional (3D) microstructures directly on
a copper plate used as the current collector for LIBs. Such an on-chip-structured
current collector avoids introducing additional layers or components,
dispenses with complex fabrication and integration, as well as provides
abundant surface structures and morphologies. It is simply combined
with mesocarbon microbeads graphite powders to form the anode electrode
of CR2032 coin half-cells. Results indicate that the prepared current
collector facilitates a high reversible discharge specific capacity
of 341.8 mAh g–1 after 200 cycles at a current rate
of 0.2 C with a capacity retention rate as high as 98.6%. This performance
is significantly higher than the traditional bare copper current collector
which maintains only 262.2 mAh g–1 with a capacity
retention rate of 79.6% at 0.2 C after 100 cycles. It is proven that
the combined microstructures of grooves, burrs, and reentrant cavities
formed on the surface of the 3D on-chip-structured current collector
effectively improve the electrochemical performance of LIBs in terms
of reversible specific capacity, cycling stability, electrical conductivity,
and Coulombic efficiency.
A new
process was proposed to reduce fine particle emissions in coal-fired
flue gases via the condensation of SO3 and water vapor.
In this new process, hot atomized water was sprayed before the electrostatic
precipitator (ESP) system to decrease the flue gas temperature and
increase the flue gas humidity, causing the flue gas temperature to
drop below the acid dew point; thus, SO3 would condense
on the particle surfaces ahead of the ESP, which would enhance the
fine particle removal efficiency of the ESP. Then, a fluoroplastic
heat exchanger was located between the ESP and the wet flue gas desulfurization
(WFGD) system to make the WFGD inlet flue gas temperature decrease
further at a high humidity, leading to the condensation of water vapor
on the particle surfaces in the desulfurization scrubber, which would
improve the removal efficiency of the WFGD. The feasibility of this
new process was analyzed by numerical calculation, and the results
showed that the new process was feasible for the original flue gas
with high SO3 concentrations, high temperature, and high
humidity. The effectiveness of this new process under typical operating
conditions was also presented. Furthermore, the influence of several
main parameters, such as the SO3 concentration of original
flue gas, the temperature drop of flue gas before the ESP, and the
temperature of flue gas at the WFGD inlet, were also investigated.
The results indicated that the fine particle emissions in the final
exhausted flue gas would be reduced by 50–70% with this new
process.
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.
BACKGROUND: The 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.
RESULTS:The 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. CONCLUSION: The 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.
RESULTS AND DISCUSSION
Feasible analysis Critical degree of supersaturation of fine particlesThe key to this process for reducing fine particle emissions by heterogeneous vapor condensation after wet desulfurization was the degree of supersaturation of the vapor phase achieved in the
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