Fouling of Heat Exchanger Tubes in Pulverized-Coal-Fired Combustion Chambers

2008 ◽  
Author(s):  
Efim Korytni ◽  
Yuli Berman ◽  
Boris Davidson ◽  
Miron Perelman ◽  
Roman Saveliev ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Power Plants ◽  
Ash Deposition ◽  
Axially Symmetric ◽  
Combustion Chambers ◽  
Weakly Bound ◽  
Water Steam ◽  
Overall Heat Transfer Coefficient ◽  
Utility Boilers ◽  
Ash Deposit

Fouling is a major concern in coal-fired power plants caused by fly ash deposit on the heat exchanger tubes that decreases the overall heat transfer coefficient to water-steam mixture. Fouling has been characterized by weakly bound-loose form, which may be removed by various methods, such as soot-blowing, blast, and sand blowing. We have carried out experimental and modeling work on fouling to develop a methodology by which the thermal conductivity of the ash deposit would be determined in a way similar to the fouling process prevailing in real systems. For that we used tubes identical in material, diameter and temperature to those used in many utility boilers. In the experimental work we placed a tube in an axially symmetric 50 kW furnace, and tested fouling from three coals, bituminous and sub-bituminous. We also developed a dynamic model for the prediction of the ash deposition growth and its heat resistance. Comparison of the model prediction and experimental results yielded satisfactory fit. Consequently, thermal resistance of heat exchanger tuber with ash deposit of those coals was determined.

A Furnace Wall Ash Monitoring System for Coal Fired Boilers

1981 ◽  
Vol 103 (3) ◽  
pp. 532-538 ◽  
Author(s):  
A. K. Chambers ◽  
J. R. Wynnyckyj ◽  
E. Rhodes
Keyword(s):  
Heat Flux ◽  
Monitoring System ◽  
Furnace Wall ◽  
Pulverized Coal ◽  
Ash Deposition ◽  
Reliable Measure ◽  
Successful Development ◽  
Utility Boilers ◽  
Ash Deposit

This paper describes the successful development of an ash-deposit monitoring system for use in large pulverized-coal fired boilers. Using commercially proven heat flux meters the system measures the severity of ash deposition by measuring the net decrease in heat flux through the boiler walls. Testing of a prototype in two Canadian Utility boilers burning Western coals has shown that the system gives a reliable measure of the cleanliness of furnace walls and of the effectiveness (or failure) of soot blowers to remove deposits. Indications are that the system will be valuable in improving efficiency of boiler operations and in minimizing slagging and fouling problems when firing difficult coals.

Methods to Define Failure Probability for Power Plant Heat Exchangers

2017 ◽  
Author(s):  
Carolyn J. John ◽  
Consuelo E. Guzman-Leong ◽  
Thomas C. Esselman ◽  
Sam L. Harvey
Keyword(s):  
Heat Exchanger ◽  
Power Plant ◽  
Fresh Water ◽  
Heat Exchangers ◽  
Power Plants ◽  
Operating Experience ◽  
Operating Conditions ◽  
Microbiologically Influenced Corrosion ◽  
Water Steam ◽  
Over Time

In response to the technical challenges faced by aging plant systems and components at nuclear power plants (NPP), the Electric Power Research Institute (EPRI) has a product entitled Integrated Life Cycle Management (ILCM). The ILCM software is a quantitative tool that supports capital asset and component replacement decision-making at NPPs. ILCM is comprised of models that predict the probability of failure (PoF) over time for various high-value components such as steam generators, turbines, generators, etc. The PoF models allow the user to schedule replacements at the optimum time, thereby reducing unplanned equipment shutdowns and costs. This paper describes a mathematical model that was developed for critical heat exchangers in a power plant. The heat exchanger model calculates the probability of the tubes, shell, or internals failing individually, and then accumulates the failures across the heat exchanger sub-components. The dominant degradation mechanisms addressed by the model include stress corrosion cracking, wear, microbiologically influenced corrosion, flow accelerated corrosion, and particle-induced erosion. The heat exchanger model combines physics-based algorithms and operating experience distributions to predict the cumulative PoF over time. The model is applicable to shell and tube heat exchangers and air-to-water heat exchangers. Many different types of fluids including open cycle fresh water, closed cycle fresh water, sea water, brackish water, air, closed cooling water, steam, oil, primary water, and condensate are included. Examples of PoF over time plots are also provided for different fluid types and operating conditions.

scholarly journals Analisa Pipa Heat Exchanger (Cooling Tube) Bervariasi Pada Turbine Guide Bearing Pembangkit Listrik Tenaga Air Siguragura

2021 ◽  
Vol 2 (2) ◽  
pp. 49-62
Author(s):  
Tambos Sianturi
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Power Plants ◽  
Paper Industry ◽  
Temperature Drop ◽  
Maximum Temperature ◽  
Cross Sectional ◽  
Overall Heat Transfer Coefficient ◽  
Cooling Tube ◽  
Rotary Type

A heat exchanger is a medium used to produce heat transfer from one fluid to another. Heat Exchanger can be used to raise the temperature or as a heater (regenerator) or lower the temperature or as a coolant (recuperator) depending on the view of heat transfer that occurs. Heat exchangers have been widely used in industries such as the chemical industry, paper industry, power plants, and other industries. In the example, each machine unit uses a heat exchanger media (especially rotary type machines) to keep the bearing temperature in normal temperature even though the unit is operated continuously or continuously. This study will analyze the temperature drop that occurs when the length of the heat exchanger pipe is added to the turbine guide bearing of PLTA Siguragura. From the research results, the maximum temperature on the guide bearing cooling tube reaches 47.3 [° C], the overall heat transfer coefficient on the guide bearing cooling tube is 98.87 [W / m²ºC], ∆Tmin on the guide bearing cooling tube installed (with 2 layers) is 14.1 [° C] and ∆Tmin which can be achieved with a cross-sectional area of ​​5.73 [m²] is 6.63 [° C]

scholarly journals Investigation of Ash Deposition Dynamic Process in an Industrial Biomass CFB Boiler Burning High-Alkali and Low-Chlorine Fuel

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1092
Author(s):  
Hengli Zhang ◽  
Chunjiang Yu ◽  
Zhongyang Luo ◽  
Yu’an Li
Keyword(s):  
Gas Flow ◽  
Circulating Fluidized Bed ◽  
Deposition Process ◽  
Biomass Combustion ◽  
Ash Deposition ◽  
Biomass Ash ◽  
Cfb Boiler ◽  
Third Stage ◽  
Ash Deposit ◽  
High Alkali

The circulating fluidized bed (CFB) boiler is a mainstream technology of biomass combustion generation in China. The high flue gas flow rate and relatively low combustion temperature of CFB make the deposition process different from that of a grate furnace. The dynamic deposition process of biomass ash needs further research, especially in industrial CFB boilers. In this study, a temperature-controlled ash deposit probe was used to sample the deposits in a 12 MW CFB boiler. Through the analysis of multiple deposit samples with different deposition times, the changes in micromorphology and chemical composition of the deposits in each deposition stage can be observed more distinctively. The initial deposits mainly consist of particles smaller than 2 μm, caused by thermophoretic deposition. The second stage is the condensation of alkali metal. Different from the condensation of KCl reported by most previous literatures, KOH is found in deposits in place of KCl. Then, it reacts with SO2, O2 and H2O to form K2SO4. In the third stage, the higher outer layer temperature of deposits reduces the condensation rate of KOH significantly. Meanwhile, the rougher surface of deposits allowed more calcium salts in fly ash to deposit through inertial impact. Thus, the elemental composition of deposits surface shows an overall trend of K decreasing and Ca increasing.

Laser Beam Welding of Open-Porous Metallic Foams for Application in Cooling Structures of Combined Cycle Power Plants

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Uwe Reisgen ◽  
Simon Olschok ◽  
Stefan Longerich
Keyword(s):  
Laser Beam ◽  
Power Plants ◽  
Laser Beam Welding ◽  
Combined Cycle ◽  
Metallic Foam ◽  
Research Centre ◽  
Combustion Chambers ◽  
Multilayer Systems ◽  
Wall Area ◽  
Graded Structures

Within the Collaborative Research Centre 561, “Thermally highly loaded, porous and cooled multilayer systems for combined cycle power plants,” open-porous and high-temperature stable Ni-based structures are being developed for the requirements of effusion cooling. A two-dimensional cooling strategy for the walls of combustion chambers, which allows the outflow of the cooling medium over the complete wall area of the combustion chamber, could be realized by an open-porous metallic foam structure. The open-porous metallic foam is produced by the “slip reaction foam sintering” process, a powder metallurgical process. To join several foams to assemble structural elements, laser beam welding has been used. Different joining strategies have been examined to find out the most suitable method to join these foams. In this paper, the process setups, settings of the different strategies, and results of trials (seam geometry and strength tests) are discussed. The need for graded structures to combine the essential permeability and adequate weldability is also shown.

Binary Particle Mixtures as a Heat Transfer Media in Shell-and-Plate Moving Packed Bed Heat Exchangers

2021 ◽  
Author(s):  
Chase Ellsworth Christen
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Particle Size ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Packed Bed ◽  
Particle Sizes ◽  
Overall Heat Transfer Coefficient ◽  
Solid Media

Solid particles are being considered in several high temperature thermal energy storage systems and as heat transfer media in concentrated solar power (CSP) plants. The downside of such an approach is the low overall heat transfer coefficients in shell-and-plate moving packed bed heat exchangers caused by the inherently low packed bed thermal conductivity values of the low-cost solid media. Choosing the right particle size distribution of currently available solid media can make a substantial difference in packed bed thermal conductivity, and thus, a substantial difference in the overall heat transfer coefficient of shell-and-plate moving packed bed heat exchangers. Current research exclusively focuses on continuous unimodal distributions of alumina particles. The drawback of this approach is that larger particle sizes require wider particle channels to meet flowability requirements. As a result, only small particle sizes with low packed bed thermal conductivities have been considered for the use in the falling-particle Gen3 CSP concepts. Here, binary particle mixtures, which are defined in this thesis as a mixture of two continuous unimodal particle distributions leading to a continuous bimodal particle distribution, are considered to increase packed bed thermal conductivity, decrease packed bed porosity, and improve moving packed bed heat exchanger performance. This is the first study related to CSP solid particle heat transfer that has considered the packed bed thermal conductivity and moving packed bed heat exchanger performance of bimodal particle size distributions at room and elevated temperatures. Considering binary particle mixtures that meet particle sifting segregation criteria, the overall heat transfer coefficient of shell-and-plate moving packed bed heat exchangers can be increased by 23% when compared to a monodisperse particle system. This work demonstrates that binary particle mixtures should be seriously considered to improve shell-and-plate moving packed bed heat exchangers.

scholarly journals OTEC Maximum Net Power Output Using Carnot Cycle and Application to Simplify Heat Exchanger Selection

Entropy ◽  
2019 ◽  
Vol 21 (12) ◽  
pp. 1143 ◽  
Author(s):  
Kevin Fontaine ◽  
Takeshi Yasunaga ◽  
Yasuyuki Ikegami
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Power Output ◽  
Heat Exchangers ◽  
Power Plants ◽  
Seawater Temperature ◽  
Carnot Cycle ◽  
Ocean Thermal Energy ◽  
Net Power Output

Ocean thermal energy conversion (OTEC) uses the natural thermal gradient in the sea. It has been investigated to make it competitive with conventional power plants, as it has huge potential and can produce energy steadily throughout the year. This has been done mostly by focusing on improving cycle performances or central elements of OTEC, such as heat exchangers. It is difficult to choose a suitable heat exchanger for OTEC with the separate evaluations of the heat transfer coefficient and pressure drop that are usually found in the literature. Accordingly, this paper presents a method to evaluate heat exchangers for OTEC. On the basis of finite-time thermodynamics, the maximum net power output for different heat exchangers using both heat transfer performance and pressure drop was assessed and compared. This method was successfully applied to three heat exchangers. The most suitable heat exchanger was found to lead to a maximum net power output 158% higher than the output of the least suitable heat exchanger. For a difference of 3.7% in the net power output, a difference of 22% in the Reynolds numbers was found. Therefore, those numbers also play a significant role in the choice of heat exchangers as they affect the pumping power required for seawater flowing. A sensitivity analysis showed that seawater temperature does not affect the choice of heat exchangers, even though the net power output was found to decrease by up to 10% with every temperature difference drop of 1 °C.

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