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.

Experimental Inverstigations On the Pressure Fluctuations in the Sealing Gap of Dry Gas Seals with Embedded Pressure Sensors

2021 ◽  
Author(s):  
Jingjing Luo ◽  
Dieter Brillert
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Static Pressure ◽  
Pressure Sensors ◽  
Operating Conditions ◽  
Test Facility ◽  
Experimental Investigations ◽  
Mechanical Seals ◽  
Process Gas ◽  
Sealing Gap

Abstract Dry gas lubricated non-contacting mechanical seals (DGS), most commonly found in centrifugal compressors, prevent the process gas flow into the atmosphere. Especially when high speed is combined with high pressure, DGS is the preferred choice over other sealing alternatives. In order to investigate the flow field in the sealing gap and to facilitate the numerical prediction of the seal performance, a dedicated test facility is developed to carry out the measurement of key parameters in the gas film. Gas in the sealing film varies according to the seal inlet pressure, and the thickness of gas film depends on this fluctuated pressure. In this paper, the test facility, measurement methods and the first results of static pressure measurements in the sealing gap of the DGS obtained in the described test facility are presented. An industry DGS with three-dimensional grooves on the surface of the rotating ring, where experimental investigations take place, is used. The static pressure in the gas film is measured, up to 20 bar and 8,100 rpm, by several high frequency ultraminiature pressure transducers embedded into the stationary ring. The experimental results are discussed and compared with the numerical model programmed in MATLAB, the characteristic and magnitude of which have a good agreement with the numerical simulations. It suggests the feasibility of measuring pressure profiles of the standard industry DGS under pressurized dynamic operating conditions without altering the key components of the seal and thereby affecting the seal performance.

A model to predict erosion on mild steel surfaces impacted by boiler fly ash particles

Wear ◽  
2004 ◽  
Vol 257 (5-6) ◽  
pp. 612-624 ◽  
Author(s):  
J.G Mbabazi ◽  
T.J Sheer ◽  
R Shandu
Keyword(s):  
Fly Ash ◽  
Mild Steel ◽  
Steel Surfaces ◽  
Boiler Fly Ash

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.

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.

Experimental Investigations on the Pressure Fluctuations in the Sealing Gap of Dry Gas Seals With Embedded Pressure Sensors

2020 ◽  
Author(s):  
Jingjing Luo ◽  
Dieter Brillert
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Static Pressure ◽  
Pressure Sensors ◽  
Operating Conditions ◽  
Test Facility ◽  
Experimental Investigations ◽  
Mechanical Seals ◽  
Process Gas ◽  
Sealing Gap

Abstract Dry gas lubricated non-contacting mechanical seals (DGS), most commonly found in centrifugal compressors, prevent the process gas flow into the atmosphere. Especially when high speed is combined with high pressure, DGS is the preferred choice over other sealing alternatives. Even though the non-contacting seal is proved reliable; the ultra-thin gas film can still lead to a host of potential problems due to possible contact. In order to investigate the flow field in the sealing gap and to facilitate the numerical prediction of the seal performance, a dedicated test facility is developed to carry out the measurement of key parameters in the gas film. Gas in the sealing film varies according to the seal inlet pressure, and the thickness of gas film depends on this fluctuated pressure. In this paper, the test facility, measurement methods and the first results of static pressure measurements in the sealing gap of the DGS obtained in the described test facility are presented. An industry DGS with three-dimensional grooves on the surface of the rotating ring, where experimental investigations take place, is used. The static pressure in the gas film is measured, up to 20 bar and 8,100 rpm, by several high frequency ultraminiature pressure transducers embedded into the stationary ring. The experimental results are discussed and compared with the numerical model programmed in MATLAB [1], the characteristic and magnitude of which have a good agreement with the numerical simulations. It suggests the feasibility of measuring pressure profiles of the standard industry DGS under pressurized dynamic operating conditions without altering the key components of the seal and thereby affecting the seal performance.

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.

Design and Computational Validation of In-Line Bare Tube Economizer for a 210 MW Pulverized Coal Fired Boiler

2013 ◽  
Author(s):  
P. R. Dhamangaonkar ◽  
Abhishek Deshmukh ◽  
Santosh Pansare ◽  
M. R. Nandgaonkar
Keyword(s):  
Fly Ash ◽  
Flue Gas ◽  
Power Plants ◽  
Gas Flow ◽  
Tube Bundle ◽  
Thermal Power ◽  
Pulverized Coal ◽  
Root Cause ◽  
Economizer Tube ◽  
Bare Tube

One of the pulverized coal fired thermal power plants in India intended to find the root cause of frequent boiler tube failures in three 210 MW units. Operation & Maintenance history and feedback from plant O&M team revealed that economizer tube failure was a frequent cause of forced outage. The plant under study used CFS (continuous fin surface) economizer with staggered tube arrangement in the 210 MW units. CFS staggered tube economizers originally appealed to many plant designers because the tortuous path created for the flue gas, enhanced heat absorption and the fins could capture heat and transfer it to the tubing. This made the CFS economizer less costly and easy for installation in a relatively small space. There is increasing use of lower quality high ash coals over the past few decades. Due to this fact an advantage of the CFS economizer design became a disadvantage. The narrow spacing in the tubes proved more susceptible to plugging and fly ash erosion. Literature study and the root cause analysis suggested that CFS staggered arrangement of economizer could be one of the prominent reason of failure of economizer tube bundle due to fly ash erosion. Flue gas flow simulation also highlighted that there is increase in velocity of flue gases across the economizer. A bare tube in-line configuration in place of existing CFS economizer was an alternative. To recommend an alternate economizer as solution, the merits of an in-line bare tube economizer were studied. Bare tubes arranged in-line are most conservative in hostile environments with high ash content, are least likely to plug, and have the lowest gas-side resistance per unit of heat transfer. A bare tube in-line economizer that can replace the existing finned tube economizer in the available space while meeting the existing design & performance parameters is recommended. An attempt was made to model & analyze the new economizer using computational fluid dynamics (CFD) tools in order to get firsthand experience and validate the results obtained using manual calculations. With limited computational resources and not so fine meshing, the performed CFD model analysis showed the expected trend but did not completely match the results.

scholarly journals Reduction of carbon monoxide emission from a solid-fuel thermo-accumulation furnace

2006 ◽  
Vol 10 (4) ◽  
pp. 107-119
Author(s):  
Dragoljub Dakic ◽  
Srdjan Belosevic ◽  
Rastko Mladenovic ◽  
Milijana Paprika ◽  
Dejan Djurovic ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Solid Fuel ◽  
Flue Gas ◽  
Emission Reduction ◽  
Gas Flow ◽  
Electric Heating ◽  
Environmental Benefits ◽  
Experimental Investigations ◽  
Fuel Quality ◽  
Carbon Monoxide Emission

Many households in Serbia, using electric thermo-accumulation furnaces for heating, have been forced to find an alternative solution, due to a significant increase in electricity prices during the last decade. A possible solution is replacing electric heating appliances with the solid fuel-fired ones. A prototype of a new concept of thermo-accumulation solid fuel-fired furnace has been developed to meet these growing needs, providing electricity saving together with considerable environmental benefits. Two strategies for reduction of carbon monoxide emission are examined in the paper: application of Pt/Al2O3 catalyst, in the form of 3 ? 0.3 mm spheres, providing further combustion of flue gases within the furnace, as well as an additional emission reduction by means of the air excess control. Experimental investigations of the catalyst influence on the conversion of carbon monoxide have been done for different operation regimes and positions of the catalyst. The paper presents selected results regarding carbon monoxide emission during wood and coal combustion. Investigations suggest a considerable effect of the catalyst and a strong influence of the catalyst position within the furnace to carbon monoxide emission reduction. In addition, experimental tests have been conducted to asses the effect of the air excess control in the furnace on carbon monoxide emission. The amount of combustion air, the flue gas flow rate, and the fuel feeding regime have been adjusted in order to keep the flue gas oxygen content in a relatively narrow range, thus obtaining controlled combustion conditions and lower carbon monoxide emission. In this way, the furnace has been made able to respond to the changes in heating needs, fuel quality and other parameters, which is advantageous in comparison with similar solid-fuel fired furnaces. .

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