scholarly journals FEATURES OF FLUE GAS CLEANING IN WET SCRUBBERS WITH VENTURI PIPE AT EXCESS SPRAYING

2018 ◽  
pp. 41-50
Author(s):  
I.A. Volchyn ◽  
V.A. Raschepkin
Keyword(s):  
Fly Ash ◽  
Flue Gas ◽  
Gas Flow ◽  
Droplet Diameter ◽  
Operating Mode ◽  
Hydrodynamic Resistance ◽  
Gas Cleaning ◽  
Wet Gas ◽  
Wet Scrubbers ◽  
Venturi Pipe

The radical increase in the density of spraying the flue gas stream in wet Venturi scrubbers allows to significantly increase the efficiency of these dust precipitators to the level of compliance with the European requirements for dust emissions. Such a shift in the operating mode significantly affects the nature of the processes of heat and mass transfer and has feature sthat are important to consider when reconstructing and designing wet gas cleaning plants. The mathematical modeling of the process of flue gas cleaning from fly ash particles in wet Venturi scrubbers in the conditions of excess spraying is performed, the dynamics of the main thermophysical parameters of the heterogeneous flow in a medium with variable moisture content and the influence of the droplet diameter on the efficiency of wet scrubbers are investigated. The problem of changing hydrodynamic resistance of a wet scrubber at different gas flow spraying densities has been studied; the effect of the input fly ash particles distribution on the result of dust cleaning is estimated. Bibl. 26, Fig. 5, Tab. 1.

scholarly journals Numerical Simulation on Double-nozzle Spray Evaporation of Desulfurization Wastewater

2021 ◽  
Author(s):  
Hong Xu ◽  
Shuqin Feng ◽  
Liehui Xiao ◽  
Yazhen Hao ◽  
Xiaoze Du
Keyword(s):  
Flue Gas ◽  
Gas Flow ◽  
Evaporation Rate ◽  
Flow Direction ◽  
Droplet Diameter ◽  
Numerical Results ◽  
Least Square ◽  
Lagrangian Model ◽  
Support Vector ◽  
Exhaust Heat

To achieve the near zero emission of wastewater in the flue gas desulfurization (FGD) system in coal-fired power plant and better utilize the exhaust heat from flue gas, a feasible technology of spraying FGD wastewater in the flue duct for evaporation is discussed in the present study. A full-scale influencing factor investigation on the wastewater droplet evaporation performance is established under the Eulerian-Lagrangian model numerically. The dominant factors, including the characters of wastewater droplets, flue gas and the spray nozzles were analyzed under different conditions, respectively. Considering the multiple factors and conditions in the process, a Least-Square support vector machine (LSSVM) model is introduced to predict the evaporation rate based on the numerical results. Conclusions are made that the flue gas temperature and droplet diameter are of great importance in the evaporation process. The spray direction of droplet parallel with the flue gas flow direction is profitable for the dispersion of droplet, resulting the maximal evaporation rate. A double-nozzle arrangement optimized with relatively small flow rate is recommended. The LSSVM model can accurately predict the evaporation rate using the numerical results with different conditions.

Numerical Prediction of Erosion of Mild Steel Surfaces by Boiler Fly Ash Particles

Volume 1 ◽  
2004 ◽  
Author(s):  
John G. Mbabazi ◽  
Thomas J. Sheer
Keyword(s):  
Fly Ash ◽  
Mild Steel ◽  
Flue Gas ◽  
Gas Flow ◽  
Erosive Wear ◽  
Test Facility ◽  
Experimental Investigations ◽  
Power Station ◽  
Erosion Rates ◽  
Steel Surfaces

Fly ash particles entrained in the flue gas from boiler furnaces in coal-fired power stations can cause serious erosive wear on steel surfaces along the downstream flow path. This paper describes research into fly ash impingement erosion on such surfaces, with particular reference to the heat transfer plates in rotary regenerative air heaters. The effect of the ash particle impact velocity and impact angle on the erosive wear of mild steel surfaces was determined through experimental investigations, using three different power station ash types. The experimental data were used to calibrate a fundamentally-derived model for the prediction of erosion rates. This erosion model was incorporated into a particle-tracking CFD flow simulation of the ash-laden flue gas flow through the complex channels between corrugated air heater plates. The predicted erosion rates were compared with measured erosion rates obtained using a large accelerated-erosion test facility located at a power station. Good agreement was obtained, the predictions generally being within 20 percent of the measured values.

scholarly journals A Pulverized Coal-Fired Boiler Optimized for Oxyfuel Combustion Technology

10.14311/1588 ◽  
2012 ◽  
Vol 52 (4) ◽  
Author(s):  
Tomáš Dlouhý ◽  
Tomáš Dupal ◽  
Jan Dlouhý
Keyword(s):  
Power Plant ◽  
Flue Gas ◽  
Gas Flow ◽  
Operating Mode ◽  
Pulverized Coal ◽  
Steam Boiler ◽  
Combustion Technology ◽  
Coal Drying ◽  
Boiler Design ◽  
Gas Recycling

This paper presents the results of a study on modifying a pulverized coal-fired steam boiler in a 250 MWe power plant for oxygen combustion conditions. The entry point of the study is a boiler that was designed for standard air combustion. It has been proven that simply substituting air by oxygen as an oxidizer is not sufficient for maintaining a satisfactory operating mode, not even with flue gas recycling. Boiler design optimization aggregating modifications to the boiler’s dimensions, heating surfaces and recycled flue gas flow rate, and specification of a flue gas recycling extraction point is therefore necessary in order to achieve suitable conditions for oxygen combustion. Attention is given to reducing boiler leakage, to which external pre-combustion coal drying makes a major contribution. The optimization is carried out with regard to an overall power plant conception for which a decrease in efficiency due to CO2 separation is formulated.

scholarly journals Mercury Removal From Coal Combustion Flue Gas by Pyrite-Modified Fly Ash Adsorbent

2021 ◽  
Author(s):  
Liqiang QI ◽  
Xu WANG ◽  
Wen WANG ◽  
Jingxin LI ◽  
Yan HUANG
Keyword(s):  
Fly Ash ◽  
Flue Gas ◽  
Coal Combustion ◽  
Gas Flow ◽  
Active Component ◽  
Mercury Removal ◽  
Gas Flow Rate ◽  
Mercury Adsorption ◽  
Mass Proportion ◽  
Modified Fly Ash

Abstract Pyrite and fly ash have certain advantages in adsorption and mercury oxidation. The pyrite-modified fly ash (PY+AC-FA) mercury adsorbent was prepared by mixing pyrite (PY) with acid-modified fly ash (AC-FA), which has better mercury removal effect than AC-FA. The experimental results of mercury adsorption show: when the reaction temperature is 50°C, the best doping proportion of modified fly ash is 20wt%, the mass proportion of pyrite to acid modified fly ash is 4:1, and the flue gas flow rate is 1.0L/min, the adsorbent has the best performance, and the adsorption rate of mercury reaches 91.92%. BET, XRD, SEM, TG-DSG and XRF were used to characterize these adsorbents. And the mechanism of mercury removal of pyrite-modified fly ash adsorbent is inferred: Hg0 is first adsorbed on the surface of the adsorbent, and then oxidized to HgS by the active component FeS2 in pyrite-modified fly ash.

Effect of CaO and Fe2O3 on Partitioning of As and S within Ash Fractions from Fluidised-Bed Co-Combustion of Coal and Wastes

2018 ◽  
Vol 11 (1) ◽  
pp. 81-90
Author(s):  
Lucie Bartoňová
Keyword(s):  
Fly Ash ◽  
Flue Gas ◽  
Coal Combustion ◽  
Bottom Ash ◽  
Correlation Coefficients ◽  
Fluidised Bed ◽  
Solid Product ◽  
Gas Cleaning

Possible interaction of volatilized As and S with CaO and Fe2O3 (creating solid product) could efficiently improve coal combustion flue gas cleaning. For this reason, S-CaO, As-CaO, S- Fe2O3 and As- Fe2O3 relationships were evaluated in bottom ash and fly ash fractions from fluidised-bed co-combustion of coal and wastes (and limestone as desulphurization additive) through calculation of correlation coefficients and composition of magnetic concentrates. It was concluded that S exhibited a dominant association with CaO while As exhibited affinity to both CaO and Fe2O3 - the significance differed a little in bottom ash and fly ash. In the bottom ash, the affinity of As to CaO was more significant, while in the fly ash the association to Fe2O3 slightly prevailed.

Predicting Fly Ash Accumulation in a Fossil Power Plant Flue Gas Duct Using Computational Fluid Dynamics

2011 ◽  
Author(s):  
S. Pal ◽  
Leonard Peltier ◽  
Mitchell Krasnopoler ◽  
Kelly J. Knight ◽  
Jonathan Berkoe
Keyword(s):  
Fluid Dynamics ◽  
Shear Stress ◽  
Fly Ash ◽  
Flue Gas ◽  
Gas Flow ◽  
Single Phase ◽  
Scale Model ◽  
Shear Stresses ◽  
Wall Shear ◽  
Fossil Power Plant

During the startup of a new fossil power plant, a high level of fly ash accumulation (higher than predicted) was encountered in the flue gas ducting upstream of a fluidized bed scrubber. The level of fly ash accumulation made it necessary to manually withdraw fly ash using a vacuum truck after short periods of operation, at less than 80% maximum continuous rating (MCR). This paper presents a simple method for rapid assessment of fly ash accumulation in flue gas ducts using steady state single phase Computational Fluid Dynamics (CFD) simulation of flue gas flow. The propensity for fly ash accumulation in a duct is predicted using calculated wall shear stresses from CFD coupled with estimates for the critical shear stresses required for mobilization of settled solids. Critical values for the mobilization stresses are determined from the Shields relations for incipient motion of particles in a packed bed with given fly ash particle size and density as inputs. Solids accumulation is possible where the wall shear stress magnitude is less than the critical shear stress for mobilization calculated from the Shields relations. Predictions of incipient fly ash accumulation based on the coupled CFD/Shields relations model correlate well with plant startup field observations. Fly ash accumulation was not observed in a related physical scale model test. A separate CFD/Shields relation analysis of the scale model physical tests show that the wall shear stresses in the scale model are several times larger than the critical value required for the mobilization of the fly ash simulant. This study demonstrates that a simple steady state, single phase CFD analysis of flue gas flow can be used to rapidly identify and address fly ash accumulation concerns in flue gas duct designs. This approach is much simpler and computationally inexpensive compared to a transient Eulerian multiphase simulation of particle laden flow involving handling the dense phase in regions of ash accumulation. Further, this study shows that physical model tests will be accurate for predicting fly ash accumulation, only if, the scaling maintains the proper ratio of wall shear stress to critical remobilization stress.

scholarly journals Using the profiled elements to increase electrocyclone effectiveness

2020 ◽  
Vol 7 (4) ◽  
pp. 173-176
Author(s):  
Anton Trinkunas ◽  
Lidia Pomortseva ◽  
Anatolii Titov ◽  
Zalina Rusinova
Keyword(s):  
Fly Ash ◽  
Flue Gas ◽  
Annular Channel ◽  
Laboratory Model ◽  
Industrial Emissions ◽  
Gas Cleaning ◽  
Cleaning Equipment

The article is devoted to flue gas cleaning, using fly ash as an example. Electrocyclone can be employed as gas-cleaning equipment. The electrocyclone operation can be intensified by reducing re-entrainment. The laboratory model of the annular channel of the electrocyclone is used to show the possibility of reducing re-entrainment by using the shaped elements of various designs on the collecting electrodes. Aerosol industrial emissions can be reduced by using an electrocyclone with modified collecting electrodes.

Numerical Study on Flow Field Distribution Regularities in Wet Gas Desulfurization Tower Changing Inlet Gas/Liquid Feature Parameters

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Qingbo Deng ◽  
Jingyu Ran ◽  
Juntian Niu ◽  
Zhongqing Yang ◽  
Ge Pu ◽  
...  
Keyword(s):  
Flow Field ◽  
Field Distribution ◽  
Flue Gas ◽  
High Speed ◽  
Gas Flow ◽  
Negative Impact ◽  
Numerical Study ◽  
Negative Influence ◽  
Wet Gas ◽  
Integration Effect

Abstract In the wet gas desulphurization tower, the uneven distribution of flue gas will have a negative impact on the desulphurization process. The effect should be counterbalanced by increasing the amount of slurry spray, which will increase the operating costs. Adding deflectors will also bring negative effects and increase the expenses. In order to avoid the negative influence, this paper studied the flow field distribution regularities of flue gas in desulfurization tower at different inlet velocities and liquid–gas ratios. Velocity field distribution character was evaluated by uniformity index. The results showed that the flue gas forms a vortex in the tower and a local high-speed gas-flow appears in the empty tower, which led to a poor flow field uniformity. After adding the spray, the flow field is integrated into uniformity. The slurry has obvious integration effect on flue gas. The lower the inlet flue gas velocity is, the higher the velocity uniform index in the desulfurization tower will be, and the heat exchange between the two phases more sufficient. To achieve the same uniformity, the less amount of slurry is required while the inlet velocity is slower. The energy consumption and material consumption of the desulfurization system can be effectively reduced by reducing the import speed reasonably.

scholarly journals AN ALTERNATIVE SOLUTION TO ESP RECONSTRUCTION FOR THE COAL FIRING THERMAL POWER PLANTS

2017 ◽  
pp. 49-55
Author(s):  
I.A. Volchyn ◽  
O.M. Kolomiets ◽  
V.A. Raschepkin
Keyword(s):  
Fly Ash ◽  
Flue Gas ◽  
Power Plants ◽  
Electrostatic Precipitator ◽  
Thermal Power ◽  
Distribution Functions ◽  
Thermal Power Plants ◽  
Particle Size Distributions ◽  
Gas Cleaning ◽  
Battery Cyclone

The mathematical modeling is performed of the efficiency of flue gas cleaning from fly ash particles of coal-fired thermal power plants, upon installation of a preliminary flue gas cleaning system that consists of a louvered dust concentrator and a battery cyclone, with the recirculation of flue gas from the battery cyclone outlet to the electrostatic precipitator pre-chamber. Based on the available experimental data for the fractional composition of fly ash downstream the boilers of coal-fired TPPs, the size distribution functions were calculated, of fly ash particles at each stage of the preliminary dust-cleaning process, as well as concentrations and modified particle size distributions, to be further used as the input data for designing options and scope of the reconstruction of existing electrostatic precipitators. Bibl. 13, Fig. 3.

Sign in / Sign up

Export Citation Format

Share Document