Corrosion Study and Modification of Superheater Tubes in a Large Mass Burn WTE Boiler (Abstract)

2005 ◽  
Author(s):  
Greg Epelbaum
Keyword(s):  
Flue Gas ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Large Mass ◽  
Operating Conditions ◽  
Cfd Model ◽  
Gas Temperature ◽  
Unique Problem ◽  
Flux Flow ◽  
Tube Metal

Essex County Resource Recovery Facility (one of American Ref-Fuel Company’s six operating plants) has processing MSW capacity of approximately 2700 TPD and about 60% of this waste comes from NY City. Therefore, availability of the Essex plant boilers is very important not only for the company’s financial performance, it is also critical for the overall garbage disposal situation in the NYC Metropolitan area. One of the main factors affecting plant availability is boiler unscheduled downtime. The most recent data show that approximately 85% of Essex boilers unscheduled downtime is caused by tube failures, the majority of which occur in the superheater tubes. These tube failures are almost exclusively caused by fireside tube metal wastage driven by complicated mechanisms of corrosion in combination with local erosion. The corrosion is caused by chloride salts in the slag that deposits on the boiler tubes, coupled with high temperatures of flue gas going through the boiler. Corrosion rates are known to be very sensitive to flue gas temperature, tube metal temperature, heat flux, flow distribution. Erosion is typically caused by high velocities and flyash particle loading and trajectories. Extensive research revealed that in addition to this typical to WTE boiler corrosion/erosion mechanism, Essex boiler superheater tubes experienced a unique problem, resulting in tube overheating, accelerated wastage, and ultimate failure. In order to address this problem a modification plan was developed, which comprised several redesign options. A specially developed Three-dimensional Computational Fluid Dynamics (3-D CFD) model was utilized for comprehensive technical evaluation of the considered design options and for predicted performance simulations of the selected design at different operating conditions. The economical analysis, conducted in conjunction with the superheater redesign, provided financial justification for this project. The project has been recently executed, and field data collection is still in progress. Some preliminary data analyses have been performed. They have shown that the boiler performance after superheater modification is very close to the predicted target simulated by the CFD model. The plant and the company are already measuring financial benefits as a result of this project, the initial phase of which is presented in this paper.

scholarly journals Reliable simple zonal method of the furnace thermal calculation

2005 ◽  
Vol 9 (2) ◽  
pp. 45-55
Author(s):  
Vladan Ivanovic
Keyword(s):  
Energy Consumption ◽  
Flue Gas ◽  
Thermal Load ◽  
Operating Conditions ◽  
Thermal Calculation ◽  
Gas Temperature ◽  
Zonal Method ◽  
One Dimensional ◽  
Furnace Performance ◽  
Steam Boilers

The calculation of the furnace in the industrial and power boilers is the most important and the most responsible part of the thermal calculation, and it has important influence on the rationalization of energy consumption. In the paper one-dimensional zonal method of the furnace thermal calculation of steam boilers is presented. It can successfully define disposition of flue gas temperature and specific thermal load of screen walls with height of the furnace in case of uneven deposits distribution which vary in size and quality. Its greatest use is for comparing furnace performance under various operating conditions.

Prediction of Raceways in a Blast Furnace

2006 ◽  
Author(s):  
Naresh K. Selvarasu ◽  
D. Huang ◽  
Zumao Chen ◽  
Mingyan Gu ◽  
Yongfu Zhao ◽  
...  
Keyword(s):  
Particle Size ◽  
Blast Furnace ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Gas Oil ◽  
Cfd Model ◽  
Coke Particle ◽  
Fuel Gas ◽  
Computational Fluid Dynamics Cfd ◽  
Insight Into

In a blast furnace, preheated air and fuel (gas, oil or pulverized coal) are often injected into the lower part of the furnace through tuyeres, forming a raceway in which the injected fuel and some of the coke descending from the top of the furnace are combusted and gasified. The shape and size of the raceway greatly affect the combustion of, the coke and the injected fuel in the blast furnace. In this paper, a three-dimensional (3-D) computational fluid dynamics (CFD) model is developed to investigate the raceway evolution. The furnace geometry and operating conditions are based on the Mittal Steel IH7 blast furnace. The effects of Tuyere-velocity, coke particle size and burden properties are computed. It is found that the raceway depth increases with an increase in the tuyere velocity and a decrease in the coke particle size in the active coke zone. The CFD results are validated using experimental correlations and actual observations. The computational results provide useful insight into the raceway formation and the factors that influence its size and shape.

scholarly journals CFD ANALYSIS OF ECONOMIZER IN A TENGENTIAL FIRED BOILER

2013 ◽  
pp. 143-147
Author(s):  
KRUNAL P. MUDAFALE ◽  
HEMANT S. FARKADE
Keyword(s):  
Flue Gas ◽  
Power Plants ◽  
Large Scale ◽  
Thermal Power ◽  
Three Dimensional ◽  
Geometrical Model ◽  
Gas Temperature ◽  
Three Dimensional Model ◽  
The Individual ◽  
Side Flow

This paper presents a simulation of the economizer zone, which allows for the condition of the shell-side flow and tube-side and tube-wall, thermal fields, and of the shell-tube heat-exchange. Selection of the economizer zone from the thermal power plant only because, it is found trends of failure that the economizer is the zone where the leakages are found more. The maximum number of cause of failure in economizer unit is due to flue gas erosion. The past failure details revels that erosion is more in U-bend areas of Economizer Unit because of increase in flue gas velocity near these bends. But it is observed that the velocity of flue gases surprisingly increases near the lower bends as compared to upper ones. The model is solved using conventional CFD techniques by STAR- CCM+ software. In which the individual tubes are treated as sub-grid features. A geometrical model is used to describe the multiplicity of heat-exchanging structures and the interconnections among them. The Computational Fluid Dynamics (CFD) approach is utilised for the creation of a three-dimensional model of the economizer coil. With equilibrium assumption applied for description of the system chemistry. The flue gas temperature, pressure and velocity field of fluid flow within an economizer tube using the actual boundary conditions have been analyzed using CFD tool. Such as the ability to quickly analyse a variety of design options without modifying the object and the availability of significantly more data to interpret the results. This study is a classic example of numerical investigation into the problem of turbulent reacting flows in large scale furnaces employed in thermal power plants for the remediation of ash deposition problems. And the experimental setup is from Chandrapur Super Thermal Power Station, Chandrapur having the unit no IV of 210 MW energy generations.

Furnace Design for Improved Exhaust Gas Circulation and Heat Transfer Efficiency

2020 ◽  
Author(s):  
Ayoola T. Brimmo ◽  
Mohamed I. Hassan Ali
Keyword(s):  
Heat Transfer ◽  
Metal Surface ◽  
Flue Gas ◽  
Waste Heat ◽  
Operating Conditions ◽  
Aluminum Production ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Exhaust Gases ◽  
Gas Circulation

Abstract In the aluminum production industry, metal furnaces are operated by diffusion flame over the metal surface to maintain the aluminum metal at the set point temperature for alloying and casting. Heat is transferred from the flame and its exhaust gases to the metal surface via radiation and convection. The exhaust gases leaves through the furnace’s chimney carrying a significant amount of waste heat to the atmosphere. Furnace efficiency could be improved by enhancing the heat transfer inside the furnace. In this study, a validated full-scale 3-D CFD model of a natural gas fired aluminum furnace is developed to investigate the effect of flue gas ventilation configurations and burner operating conditions on the heat transfer inside the furnace. Onsite measurements are carried out for the fuel and airflow rates as well as flue gas temperature. Four flue ventilation configurations are considered with eight furnace’s operation modes. The flue-gas’s waste-heat varies from 49–58%, with the highest value occurring at the high-fire operating mode. This indicates a significant room for improvement in the furnace performance. Results suggest that a symmetrical positioning of the exhaust duct favors effective exhaust gas circulation within the furnace and hence, increases hot-gases’ heat-transfer effectiveness inside the furnace. These results provide some guidelines for optimal aluminum reverberatory furnace designs and operation.

Three-Dimensional Numerical Modeling of Stoker-Fired Power Boilers

1999 ◽  
Author(s):  
Scott A. Dudek ◽  
Richard A. Wessel ◽  
Joseph R. Strempek
Keyword(s):  
Gas Flow ◽  
Waste Treatment ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Unburned Carbon ◽  
Air Distribution ◽  
Gas Temperature ◽  
Operational Parameters ◽  
Complete Combustion ◽  
Power Boiler

Abstract A numerical model has been developed to simulate the various interacting physical processes that occur within any stoker-fired power boiler burning wood, refuse-derived fuel (RDF), coal, or other biomass fuel and operating at steady state. The processes modeled are three-dimensional turbulent gas flow, particle motion (including dispersion and re-entrainment), heterogeneous and homogeneous chemical reactions, and heat transfer. The purpose of this paper is to provide a detailed description of the model and to present an example of its use. The model can be used as a cost-effective tool to assist in the design of original and retrofit power boiler equipment and in the diagnosis and resolution of boiler operating problems. The effects of modifying operational parameters or the physical arrangement of equipment can be quickly evaluated. Simulations can be used to optimize overfire air distribution and arrangement to produce a more uniform gas flow distribution within the furnace, resulting in more complete combustion and less particulate carryover. As an example of the model’s capability, simulations were produced for a stoker-fired power boiler using wood, bark-pile reclaim, and waste-treatment sludge for fuel. The results show that changes in the air distribution and in the arrangement of operational overfire air ports can produce a significant reduction in carbon monoxide, unburned carbon loss, and particulate carryover, without increasing furnace exit gas temperature. Field modifications as a result of the modeling study have improved boiler operation and eliminated tube failures caused by flyash erosion.

Solution of Cavitation Problems in Pumps by Means of Model Air Testing

1965 ◽  
Vol 2 (04) ◽  
pp. 422-430
Author(s):  
K. Pilarczyk ◽  
Vasil Rusak
Keyword(s):  
Centrifugal Pump ◽  
Radial Direction ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Operating Conditions ◽  
Original Design ◽  
Velocity Pattern ◽  
Standard Values ◽  
Suction Nozzle ◽  
Dimensional Picture

This paper describes a case of rather unusual and severe cavitation in a double-suction centrifugal pump and the way the problem was corrected. The cavitation was demonstrated in a heavy erosion in the impeller blades while the performance of the pump did not show any signs of deterioration. The original design of the pump and the operating conditions were rather conventional with the available NPSH exceeding the recommended Hydraulic Institute Standard values. To solve this problem it was necessary to study, in detail, the velocity pattern at the impeller inlet. For this purpose, a wooden model of the pump suction nozzle was built and tested with air. A three-dimensional picture of the flow distribution in the impeller eye was obtained from this test indicating a considerable nonunlformlty in both the circumferential and the radial direction. This information led to the redesign of the impeller-inlet passage which ultimately eliminated the cavitation.

Experimental and Numerical Investigation of the Flow in a Low-Pressure Industrial Steam Turbine With Part-Span Connectors

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Markus Häfele ◽  
Christoph Traxinger ◽  
Marius Grübel ◽  
Markus Schatz ◽  
Damian M. Vogt ◽  
...  
Keyword(s):  
Flow Field ◽  
Steam Turbine ◽  
Numerical Study ◽  
Three Dimensional ◽  
Low Pressure ◽  
Operating Conditions ◽  
Engineering Practice ◽  
Cfd Model ◽  
Wide Range ◽  
The Impact

An experimental and numerical study on the flow in a three-stage low-pressure (LP) industrial steam turbine is presented and analyzed. The investigated LP section features conical friction bolts in the last and a lacing wire in the penultimate rotor blade row. These part-span connectors (PSC) allow safe turbine operation over an extremely wide range and even in blade resonance condition. However, additional losses are generated which affect the performance of the turbine. In order to capture the impact of PSCs on the flow field, extensive measurements with pneumatic multihole probes in an industrial steam turbine test rig have been carried out. State-of-the-art three-dimensional computational fluid dynamics (CFD) applying a nonequilibrium steam (NES) model is used to examine the aerothermodynamic effects of PSCs on the wet steam flow. The vortex system in coupled LP steam turbine rotor blading is discussed in this paper. In order to validate the CFD model, a detailed comparison between measurement data and steady-state CFD results is performed for several operating conditions. The investigation shows that the applied one-passage CFD model is able to capture the three-dimensional flow field in LP steam turbine blading with PSC and the total pressure reduction due to the PSC with a generally good agreement to measured values and is therefore sufficient for engineering practice.

Development of a Two-Dimensional Computational Fluid Dynamics Approach for Computing Three-Dimensional Honeycomb Labyrinth Leakage

2004 ◽  
Vol 126 (4) ◽  
pp. 794-802 ◽  
Author(s):  
Dong-Chun Choi ◽  
David L. Rhode
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Three Dimensional ◽  
Labyrinth Seal ◽  
Operating Conditions ◽  
Two Dimensional ◽  
Cfd Model ◽  
Resource Requirement ◽  
Three Dimensional Flow ◽  
Dimensional Flow

A new approach for employing a two-dimensional computational fluid dynamics (CFD) model to approximately compute a three-dimensional flow field such as that in a honeycomb labyrinth seal was developed. The advantage of this approach is that it greatly reduces the computer resource requirement needed to obtain a solution of the leakage for the three-dimensional flow through a honeycomb labyrinth. After the leakage through the stepped labyrinth seal was measured, it was used in numerically determining the value of one dimension (DTF1) of the simplified geometry two-dimensional approximate CFD model. Then the capability of the two-dimensional model approach was demonstrated by using it to compute the three-dimensional flow that had been measured at different operating conditions, and in some cases different distance to contact values. It was found that very close agreement with measurements was obtained in all cases, except for that of intermediate clearance and distance to contact for two sets of upstream and downstream pressure. The two-dimensional approach developed here offers interesting benefits relative to conventional algebraic-equation models, particularly for evaluating labyrinth geometries/operating conditions that are different from that of the data employed in developing the algebraic model.

Numerical Study the NOx Emission Characteristics of 600MW Opposed Swirling Coal-Fired Utility Boiler

2014 ◽  
Vol 1010-1012 ◽  
pp. 847-855
Author(s):  
Ya Ming Liu ◽  
Fang Yong Li ◽  
Qi Sheng Xu
Keyword(s):  
Fly Ash ◽  
Carbon Content ◽  
Residence Time ◽  
Flue Gas ◽  
Pulverized Coal ◽  
Nox Emission ◽  
Emission Characteristics ◽  
Cfd Model ◽  
Gas Temperature ◽  
Coal Particles

In this paper, a computational fluid dynamics (CFD) model of a 600 MW opposed swirling coal-fired utility boiler has been established to numerically study the NOx emission characteristics under different ratios of over fire air (OFA) and modes of in-service burner layers. The current CFD model had adopted a chemical percolation devolatilization (CPD) model and been validated by comparing the simulated results with the experimental data. The numerical simulation results show that, with increasing the ratio of OFA, the carbon content in fly-ash increase somewhat linearly and the NOx emission reduce significantly, and the OFA ratio of 30% is optimal with higher burnout of pulverized coal and lower NOx emission. The different in-service burner layer modes have different influences on the residence time of the pulverized-coal particles, effect of air staging in the burner region and flue gas temperature at the exit of the lower furnace. Stopping the upper burner layers can increases the residence time of the pulverized-coal particles, resulting in the reduction of the carbon content in the fly ash and the increase of the pulverized-coal burnout. The flue gas temperature at the exit of the lower furnace can also decrease, which would be helpful to reducing the slagging tendency on the surfaces of the platen superheaters.

Numerical Simulation of Complex Air Flow in an Aeroengine Gear Box

2009 ◽  
Author(s):  
Zixiang Sun ◽  
John W. Chew ◽  
Neil Fomison
Keyword(s):  
Porous Media ◽  
Test Data ◽  
Air Flow ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Cfd Model ◽  
Complex Flow ◽  
Pressure Loss Coefficient ◽  
Geometry Modeling ◽  
Gear Box

The internal gear box (IGB) of an aeroengine represents a severe challenge in computational fluid dynamics (CFD). In the present study, an axisymmetric CFD model was assessed to investigate the complex internal air flow in an aeroengine IGB. All the non-axisymmetric components and geometry features inside the gear box, such as bearings, gears, bolts and slots, as well as the radial drive system and vent pipes, were simulated using porous media models. Their flow resistance was estimated either by empirical correlations or by preparatory CFD studies and comparison with measurements. To evaluate the CFD technique adopted in the present investigation, a separate bolt windage study was conducted using a similar axisymmtric CFD model with the porous media approach. Good agreement of the bolt windage with other workers’ rig test data was observed. The present application of the porous media approach into a complex gear box flow represents a first attempt to use state of art CFD to assist an industrial design. Both maximum take-off (MTO) and ground idle (GI) running conditions were investigated. The complex flow patterns in the gear box were obtained. The results show a similar dimensionless performance of intermediate pressure (IP) and high pressure (HP) gears between the two operating conditions. For the present gear box arrangement under investigation, the CFD results suggest that the airflows induced by the HP gear and HP bearing are higher than their IP counterparts. A comparison with power absorption rig test data for the similar HP crownwheel in isolation shows that an assumption of pressure loss coefficient of 10 for the porous media of bevel gears may be appropriate, as the HP gear torque coefficient obtained in the CFD prediction is equal to 0.05, very close to its expected value. In addition, the effects of an assumed stationary IP gear and a large seal clearance on the HP gear performance were also investigated. The numerical results show that their impacts are insignificant, probably due to the strong pumping effects of the HP gear. Further discussion on the possible influence of the airflow on the oil motion within the gearbox and assistance to improve the traditional internal airflow models used for bearing chamber sealing analysis was also made. Three dimensional geometry modeling and inclusion of the oil phase are considered feasible. Such further investigations would aid the understanding of the interaction between the induced airflow due to the rotating components and oil motion, and their impact on oil scavenging behaviour and ‘windage’ contribution to heat oil.

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