Modeling of Superheater Operation in a Steam Boiler

2014 ◽  
Author(s):  
Marcin Trojan ◽  
Dawid Taler ◽  
Jan Taler ◽  
Piotr Dzierwa
Keyword(s):  
Flue Gas ◽  
Tube Wall ◽  
Numerical Technique ◽  
Operating Conditions ◽  
Outlet Temperature ◽  
Steam Boiler ◽  
Steam Temperature ◽  
Additional Increase ◽  
Internal Surfaces ◽  
The Impact

A numerical method for modeling actual steam superheaters is presented. The finite volume method was used to determine flue gas, tube wall and steam temperature. The numerical technique presented in the paper can especially be used for modeling boiler superheaters with a complex tube arrangement when detail information on the tube wall temperature distribution is needed. The method of modeling the superheater can be used both in the design, performance as well as in upgrading the superheaters. If the steam temperature at the outlet of the superheater is too low or too high, the designed outlet temperature can be achieved by changing a flow arrangement of the superheater. For example, the impact of the change of the counter to parallel flow or to mixed flow can be easily assessed. The presented method of modeling is a useful tool in analyzing the impact of the internal scales or outer ash fouling on the superheater operating conditions. Both ash deposits at the external and scales at the internal surfaces of the tubes contribute to the reduction of the steam temperature at the outlet of the superheater. Furthermore, scale deposits on the inner surface of the tubes cause a significant temperature rise and may lead to the tube damage. The higher temperature of the flue gas over a part of parallel superheater tubes increases the steam temperature and decreases steam mass flow rate through the tubes with excessive heating. This results in an additional increase in the steam temperature at the outlet of the superheater.

scholarly journals Effect of scale deposits on the internal surfaces of the tubes on the superheater operation

2013 ◽  
Vol 34 (4) ◽  
pp. 73-91 ◽  
Author(s):  
Marcin Trojan ◽  
Jan Taler
Keyword(s):  
Temperature Distribution ◽  
Wall Temperature ◽  
Flue Gas ◽  
Tube Wall ◽  
Heat Flow Rate ◽  
Gas Temperature ◽  
Steam Temperature ◽  
Internal Surfaces ◽  
Tube Wall Temperature ◽  
Scale Deposits

Abstract A mathematical model of the steam superheater exchanger with distributed parameters has been developed. Scale deposits were assumed to be present on the internal tube surfaces. It was assumed that the inner tube surfaces are covered by a thin layer of scale deposits. The finite volume method was used to solve partial differential equations describing flue gas, tube wall and steam temperature. The developed modeling technique can especially be used for modeling tube heat exchangers when detail information on the tube wall temperature distribution is needed. The numerical model of the superheater developed in the paper can be used for modeling of the superheaters with complex flow arrangement accounting scales on the internal tube surfaces. Using the model proposed the detailed steam, wall and flue gas temperature distribution over the entire superheater can be determined. The steam pressure distribution along its path flow and the total heat transfer rate can also be obtained. The calculations showed that the presence of scale on the internal surfaces of the tubes cause the steam temperature decrease and the heat flow rate transferred from the flue gas to the steam. Scale deposits on the inner surfaces of the tubes cause the tube wall temperature growth and can lead to premature wear of tubes due to overheating.

A parametric study of the impact of membrane materials and process operating conditions on carbon capture from humidified flue gas

2013 ◽  
Vol 431 ◽  
pp. 139-155 ◽  
Author(s):  
Bee Ting Low ◽  
Li Zhao ◽  
Timothy C. Merkel ◽  
Michael Weber ◽  
Detlef Stolten
Keyword(s):  
Flue Gas ◽  
Parametric Study ◽  
Carbon Capture ◽  
Operating Conditions ◽  
Membrane Materials ◽  
The Impact

Dew Point of the Flue Gas of Boilers Co-Firing Biomass with Coal

2013 ◽  
Vol 34 (1) ◽  
pp. 101-108 ◽  
Author(s):  
Szymon Ciukaj ◽  
Marek Pronobis
Keyword(s):  
Regression Analysis ◽  
Moisture Content ◽  
Flue Gas ◽  
Large Scale ◽  
Fuel Mixture ◽  
Dew Point ◽  
Outlet Temperature ◽  
Utility Boilers ◽  
Boiler Efficiency ◽  
The Impact

Abstract The paper deals with the impact of co-firing biomass with coal in boilers on the dew point of the flue gas. Co-firing of biomass may have twofold implications on corrosion and fouling, which are the processes that determine the lowest acceptable flue gas outlet temperature and as a result, boiler efficiency. Both phenomena may be reduced by co-firing of usually low sulphur biomasses or enhanced due to increased moisture content of biomass leading to increased water dew point. The present study concerns the problem of low-temperature corrosion in utility boilers. The paper gives (in the form of diagrams and equations) a relationship between water dew point and moisture content of fuel mixture when co-firing coal and various biomasses. The regression analysis shows that despite significant differences in the characteristics of coals and these of additional fuels, which are planned for co-firing in large-scale power boilers, the water dew point can be described by a function given with the accuracy, which shall be satisfactory for engineering purposes. The discussion of the properties of biofuels indicates that the acid dew point surplus over the water dew point (Δtr = tr - twr) is not likely to exceed 10 K when co-firing biomass. The concluding remarks give recommendations for the appropriate operation of boilers in order to reduce risks associated with biomass co-combustion.

Structural Design Considerations for Tubular Power Tower Receivers Operating at 650°C

2014 ◽  
Author(s):  
Ty W. Neises ◽  
Michael J. Wagner ◽  
Allison K. Gray
Keyword(s):  
Carbon Dioxide ◽  
High Pressure ◽  
Supercritical Carbon Dioxide ◽  
Performance Metrics ◽  
Operating Conditions ◽  
Design Parameters ◽  
Outlet Temperature ◽  
Power Cycles ◽  
The Impact ◽  
Supercritical Carbon

Research of advanced power cycles has shown supercritical carbon dioxide power cycles may have thermal efficiency benefits relative to steam cycles at temperatures around 500–700°C. To realize these benefits for CSP, it is necessary to increase the maximum outlet temperature of current tower designs. Research at NREL is investigating a concept that uses high-pressure supercritical carbon dioxide as the heat transfer fluid to achieve a 650°C receiver outlet temperature. At these operating conditions, creep becomes an important factor in the design of a tubular receiver and contemporary design assumptions for both solar and traditional boiler applications must be revisited and revised. This paper discusses lessons learned for high-pressure, high-temperature tubular receiver design. An analysis of a simplified receiver tube is discussed, and the results show the limiting stress mechanisms in the tube and the impact on the maximum allowable flux as design parameters vary. Results of this preliminary analysis indicate an underlying trade-off between tube thickness and the maximum allowable flux on the tube. Future work will expand the scope of design variables considered and attempt to optimize the design based on cost and performance metrics.

Impact of Fuel Flexibility Needs on a Selected GT Performance in IGCC Application

2012 ◽  
Author(s):  
Mohammad Mansouri Majoumerd ◽  
Peter Breuhaus ◽  
Jure Smrekar ◽  
Mohsen Assadi ◽  
Carmine Basilicata ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Operating Conditions ◽  
Parameter Study ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Lumped Model ◽  
Surge Margin ◽  
Fuel Flexibility ◽  
Compressor Inlet ◽  
The Impact

As part of a European Union (EU) funded H2-IGCC project, a baseline IGCC power plant was established; this was presented at the ASME Turbo Expo 2011 (GT2011-45701). The current paper focuses on a detailed investigation of the impact of using various fuels considering different operating conditions on the gas turbine performance, and the identification of technical solutions for the realization of the targeted fuel flexibility. Using a lumped model, based on real engine data, compressor and turbine maps of the targeted engine were generated and implemented into the detailed GT model made in the commercial heat and mass balance program, IPSEpro. The implementation was done in terms of look-up tables. The impact of fuel change on the gas turbine island has been investigated and reported in this paper. Calculation results show that for the given boundary conditions, the surge margin of the compressor was slightly reduced when natural gas was replaced by hydrogen-rich syngas. The use of cleaned syngas instead of hydrogen-rich syngas resulted in a considerable reduction of the surge margin and elevation of the turbine outlet temperature (TOT) at design point conditions, when keeping the turbine inlet temperature (TIT) and compressor inlet mass flow unchanged. To maintain the TOT and improve the surge margin, when operating the engine with cleaned syngas, a combination of adjustment of variable inlet guide vanes (VIGV) and reduced TIT was considered. A parameter study was carried out to provide better understanding of the current limitations of the engine and to identify possible modifications to improve fuel flexibility.

ANN - SQP Approach For NOx Emission Reduction In Coal Fired Boilers

2012 ◽  
Vol 13 (3) ◽  
Author(s):  
Ilamathi Balamurugan ◽  
Selladurai V. Gounder ◽  
Balamurugan Kulendran
Keyword(s):  
Flue Gas ◽  
Field Experiments ◽  
Fitness Function ◽  
Load Condition ◽  
Operating Conditions ◽  
Nox Emission ◽  
Optimum Level ◽  
Outlet Temperature ◽  
Boiler Load ◽  
Feed Forward Back Propagation

Abstract In this research paper, predictive modelling of NOx emission of a 210 MW capacity pulverized coal-fired boiler and combustion parameter optimization to reduce NOx emission in flue gas is proposed. The effects of oxygen concentration in flue gas, coal properties, coal flow, boiler load, air distribution scheme, flue gas outlet temperature and nozzle tilt were studied. The data collected from parametric field experiments were used to build a feed-forward back-propagation artificial neural net (ANN). The coal combustion parameters were used as inputs and NOx emission as outputs of the model. The ANN model was developed for full load condition and its predicted values were verified with the actual values. The algebraic equation containing weights and biases of the trained net was used as fitness function in sequential quadratic programming (SQP) to find the optimum level of input operating conditions for low NOx emission. The results proved that the proposed approach could be used for generating feasible operating conditions.

scholarly journals Generalized Energy and Ecological Characteristics of the Process of Co-Firing Coal with Biomass in a Steam Boiler

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2634
Author(s):  
Joachim Kozioł ◽  
Joanna Czubala ◽  
Michał Kozioł ◽  
Piotr Ziembicki
Keyword(s):  
Structural Parameters ◽  
Point Of View ◽  
Operating Conditions ◽  
Hard Coal ◽  
Steam Boiler ◽  
Ecological Characteristics ◽  
Steam Boilers ◽  
Gross Energy ◽  
Harmful Substances ◽  
The Impact

One of the ways used to reduce the emission of carbon dioxide and other harmful substances is the implementation of biomass co-firing processes with coals. Such processes have been implemented for many years throughout many countries of the world, and have included using existing high-power coal boilers. Despite numerous experiments, there are still no analyses in the literature allowing for their generalization. The purpose of this paper is to determine the generalized energy and ecological characteristics of dust steam boilers co-firing hard coal with biomass. The energy characteristics determined in the paper are the dependence of the gross energy efficiency of boilers on such decision parameters as their efficiency and the share of biomass chemical energy in fuel. However, the ecological characteristics are the dependence of emission streams: CO, NOx, SO2, and dust on the same decision parameters. From a mathematical point of view, the characteristics are approximation functions between the efficiency values obtained from the measurements and the emission streams of the analysed harmful substances and the corresponding values of the decision parameters. Second-degree polynomials are assumed in this paper as approximation functions. Therefore, determining the characteristics came down to determining the constant coefficients occurring in these polynomials, the so-called structural parameters. The fit of the determined characteristics was assessed based on the coefficients of random variation and the test of estimated significance of structural parameters. Boiler characteristics can be used when forecasting the impact of changes in operating conditions on the effects achieved in existing, modernized, and designed boilers. The generalization of the characteristics was obtained from the measurement results presented in 10 independent sources used to determine them.

Flue Gas Recirculation of the Alstom Sequential Gas Turbine Combustor Tested at High Pressure

2011 ◽  
Author(s):  
Felix Guethe ◽  
Dragan Stankovic ◽  
Franklin Genin ◽  
Khawar Syed ◽  
Dieter Winkler
Keyword(s):  
High Pressure ◽  
Gas Turbine ◽  
Flue Gas ◽  
Operating Conditions ◽  
Limiting Factors ◽  
Combustion System ◽  
Flue Gas Recirculation ◽  
Wide Range ◽  
Gas Recirculation ◽  
The Impact

Concerning the efforts in reducing the impact of fossil fuel combustion on climate change for power production utilizing gas turbine engines Flue Gas Recirculation (FGR) in combination with post combustion carbon capture and storage (CCS) is one promising approach. In this technique part of the flue gas is recirculated and introduced back into the compressor inlet reducing the flue gas flow (to the CCS) and increasing CO2 concentrations. Therefore FGR has a direct impact on the efficiency and size of the CO2 capture plant, with significant impact on the total cost. However, operating a GT under depleted O2 and increased CO2 conditions extends the range of normal combustor experience into a new regime. High pressure combustion tests were performed on a full scale single burner reheat combustor high-pressure test rig. The impact of FGR on NOx and CO emissions is analyzed and discussed in this paper. While NOx emissions are reduced by FGR, CO emissions increase due to decreasing O2 content although the SEV reheat combustor could be operated without problem over a wide range of operating conditions and FGR. A mechanism uncommon for GTs is identified whereby CO emissions increase at very high FGR ratios as stoichiometric conditions are approached. The feasibility to operate Alstom’s reheat engine (GT24/GT26) under FGR conditions up to high FGR ratios is demonstrated. FGR can be seen as continuation of the sequential combustion system which already uses a combustor operating in vitiated air conditions. Particularly promising is the increased flexibility of the sequential combustion system allowing to address the limiting factors for FGR operation (stability and CO emissions) through separated combustion chambers.

Remnant Life Assessment of Platformer Heater T9 Tubes Using API 579 Omega Method

2007 ◽  
Author(s):  
Ohgeon Kwon ◽  
Charles Thomas ◽  
David Knowles ◽  
Andrew Saunders-Tack
Keyword(s):  
Material Properties ◽  
Operating Conditions ◽  
Life Assessment ◽  
Outlet Temperature ◽  
Remaining Life ◽  
Process Gas ◽  
Omega Method ◽  
The Difference ◽  
Operational Envelope ◽  
The Impact

Tubes operated in furnaces are known to suffer from damage as a result of time dependent strain, i.e. creep. As such there is a need to predict remaining life. The MPC Omega Method has been adopted by API (API 579 “Fitness for Service”) as the standard method of life assessment and has been used to perform a remnant life assessment on a platformer furnace. Samples of T9 tubes were removed from the heater based on site inspection to determine the levels of strain. This inspection was undertaken after 224,000 hours operation at a process gas outlet temperature of 540°C. The uncertainty caused by the difference in life based either on minimum and mean material properties, indicates the necessity of proceeding to a Level 3 assessment in order to determine the actual material properties. The results of this approach using the API 579 Omega method demonstrated that the hot face material had properties within the scatter band, mid-way between the mean and minimum data lines and provided confidence as to the remaining life. The Omega approach successfully allowed the impact of variations in future operating conditions to be explored providing information to set the operational envelope and define inspection and replacement strategies.

Lab-Scale Study on Fireside Superheaters Corrosion in MSWI Plants

2009 ◽  
Author(s):  
Jean-Michel Brossard ◽  
Florimonde Lebel ◽  
Christophe Rapin ◽  
Jean-Franc¸ois Mareˆche´ ◽  
Xavier Chaucherie ◽  
...  
Keyword(s):  
Flow Pattern ◽  
Flue Gas ◽  
Gas Flow ◽  
Operating Conditions ◽  
Gas Temperature ◽  
Steam Temperature ◽  
Corrosion Tests ◽  
Corrosion Rates ◽  
First Results

Combustion of the municipal waste generates highly corrosive gases (HCl, SO2, NaCl, KCl and heavy metals chlorides) and ashes containing alkaline chlorides and sulphates. Currently, corrosion phenomena are particularly observed on superheater’s tubes. Corrosion rates depend mainly on installation design, operating conditions i.e. gas and steam temperature and velocity of the flue gas containing ashes. This paper presents the results obtained using an innovative laboratory-scale corrosion pilot, which simulates MSWI boilers conditions characterized by a temperature gradient at metal tube on the presence of corrosive gases and ashes. The presented corrosion tests were realized on carbon steel at fixed metal temperature (400°C). The influence of the flue gas temperature, synthetic ashes composition and flue gas flow pattern were investigated. After corrosion test, cross section of tube samples were characterised to evaluate thickness loss and estimate corrosion rate while the elements present in corrosion layers were analysed. Corrosion tests were carried out twice in order to validate the accuracy and reproducibility of results. First results highlight the key role of molten phase related to the ash composition and flue gas temperature as well as the deposit morphology, related to the flue gas flow pattern, on the mechanisms and corrosion rates.

Sign in / Sign up

Export Citation Format

Share Document