Corrosion of Superheaters and Reheaters of Pulverized-Coal-Fired Boilers, II

1961 ◽  
Vol 83 (4) ◽  
pp. 468-474 ◽  
Author(s):  
Carl Cain ◽  
Wharton Nelson
Keyword(s):  
High Temperature ◽  
Liquid Phase ◽  
Gas Phase ◽  
Coal Ash ◽  
Pulverized Coal ◽  
Corrosion Mechanism ◽  
Fireside Corrosion ◽  
Factors Affecting ◽  
Ferritic Alloys ◽  
Tube Metal

This paper deals with studies of high-temperature fireside corrosion of reheater and superheater tubes in pulverized-coal-fired boilers. Factors affecting the temperature range and rate of corrosion by molten complex alkali sulfates are described. The influence of sulfides, produced by reaction of complex sulfates with tube metal, on corrosion rate is discussed. The similarity of coal-ash to oil-ash corrosion mechanism is brought out. Methods for distinguishing liquid phase from gas-phase corrosion on ferritic alloys are presented.

scholarly journals The Deposit Formation Mechanism in Coal-Fired Rotary Kiln for Iron Ore Pellet Production: A Review

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 974
Author(s):  
Shuai Wang ◽  
Yufeng Guo ◽  
Kuo Liu ◽  
Zhuang Yang ◽  
Yajing Liu ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Alkali Metal ◽  
Alkali Metals ◽  
Iron Ore ◽  
Coal Ash ◽  
Pulverized Coal ◽  
Efficient Production ◽  
Material Base ◽  
Deposit Formation ◽  
Rotary Kilns

The deposit-forming problem is one of the main bottlenecks restricting the yield and production benefit of iron ore pellets produced by coal-fired rotary kilns. In order to implement measures to ensure the efficient production of pellets by coal-fired rotary kilns, the mechanism and influencing factors on the deposit formation were reviewed. The pellet powder and coal ash come together to form the material base of the deposit. Meanwhile, the local reducing atmosphere caused by the continued combustion of residual carbon increases the FeO content, resulting in the formation of low-melting-point silicates. Moreover, alkali metal elements in coal ash can also promote liquid phase formation to cause serious deposit aggregation problems. During high-temperature roasting, the liquid phase corrodes the surface of the refractory brick to form the initial deposit, whereafter, it binds the pellet powder and coal ash from the material layer, which causes the deposit to accumulate continuously. The deposit formation of coal-fired rotary kilns is the result of interaction between many factors, which includes the quality of the green pellets, the composition of coal ash, the combustion efficiency of pulverized coal, roasting temperature, FeO content and alkali metal input. Finally, it is recommended that some measures to mitigate deposit formation can be adopted, such as increasing the compression strength of preheated pellets, choosing high-quality raw materials with low alkali metals, improving the combustion of pulverized coal.

scholarly journals A preliminary examination of fluid inclusions in nepheline, sorensenite, tugtupite and chkalovite from the Ilímaussaq alkaline intrusion, South Greenland

1970 ◽  
Vol 81 ◽  
pp. 1-41
Author(s):  
V.S Sobolev ◽  
T.Y Bazarova ◽  
N.A Shugurova ◽  
N.Sh Bazarov ◽  
Y.A Dolgov ◽  
...  
Keyword(s):  
High Temperature ◽  
Liquid Phase ◽  
Gas Phase ◽  
Fluid Inclusions ◽  
Solid Phase ◽  
Inert Gases ◽  
Preliminary Examination ◽  
Alkaline Intrusion ◽  
Primary Inclusion ◽  
Academy Of Sciences

A preliminary examination has been undertaken of fluid inclusions in four minerals from the Ilímaussaq alkaline intrusion. The apparatus used in the study has been developed in the Institute of Geology and Geophysics of the Siberian Branch of the Academy of Sciences, Novosibirsk. Primary three-phase inclusions (liquid-gas-crystals) in nepheline from naujaite homogenize in the liquid phase at 850-1040° C. The gas phase in one analysed inclusion is dominated by CO2. Primary gas-liquid inclusions in nepheline from green lujavrite homogenize at 910-970° C in the liquid phase. These temperatures are in agreement with temperatures obtained on nephelines from Lovozero, Miask and Synnur and with data from fusion experiments on the rocks in question. Primary gas-liquid inclusions in sorensenite and tugtupite from late analcimealbite veins homogenize at 400-460° C. The liquid phase of fluid inclusions in tugtupite contains 21 weight per cent of salts -sodium chloride is assumed to be predominant. The gas phase in one primary inclusion in tugtupite is dominated by CO2. Secondary fluid inclusions in the two minerals homogenize at 350-100° C. The temperatures obtained are in agreement with those estimated from mineralogical evidence. A big crystal of chkalovite from an ussingite-analcime vein contains several generations of fluid inclusions. The primary liquid-gas-crystal inclusions homogenize at 860-980° C. The solid phase is dissolved at 330-360° C, two immiscible liquids appear at 700-800° C. Half of the ca. 250 fluid inclusions examined belong to this category. The several generations of secondary inclusions which embrace liquid-gascrystal inclusions, gas-liquid inclusions and gas inclusions homogenize in several groups between 760°C and 100°C. The liquid phase of the high temperature inclusions contains 40-44 weight per cent NaCI. The pressure at the temperature of homogenization is estimated to be higher than 1000 atm. The gas phase is dominated by CO2 and N2 + inert gases. The unexpectedly high temperature of homogenization of the primary inclusions of the chkalovite is difficult to explain. A detailed study of this problem is in preparation.

High Temperature Corrosion Behavior of Si-Containing Alloys in the Liquid Phase of Na2SO4 25.7 Mass% NaCl

2012 ◽  
Vol 323-325 ◽  
pp. 353-358 ◽  
Author(s):  
Toto Sudiro ◽  
Tomonori Sano ◽  
Shoji Kyo ◽  
Osamu Ishibashi ◽  
Masaharu Nakamori ◽  
...  
Keyword(s):  
High Temperature ◽  
Liquid Phase ◽  
Corrosion Behavior ◽  
High Temperature Corrosion ◽  
Corrosion Mechanism ◽  
Plasma Sintering ◽  
Ni Addition ◽  
Spark Plasma ◽  
Si Content ◽  
Conicraly Alloy

The high temperature corrosion behavior of Si-containing alloys consisting of Cr-Si-Ni and CoNiCrAlY-Si alloys fabricated by spark plasma sintering technique was investigated in the liquid phase of Na2SO4 + 25.7 mass% NaCl at temperatures ranging from 923-1273 K. The purpose of this study is to develop excellent corrosion resistant alloys for coating applications. Our experimental results show the CrSi2 alloy with 10 mass% Ni content and the CoNiCrAlY alloy with 30 mass% Si content are the most promising materials for applications in this atmosphere. This is due to the formation of a protective SiO2 and Al2O3/SiO2 scale, respectively. The formation of a dense and continuous oxide layer composed and/or consisted of SiO2 plays a significant role in hindering the inward diffusion of chlorine and sulfur to the alloys substrate. Particularly, the corrosion mechanism of Cr-Si-Ni alloys and the influence of Ni addition on the corrosion resistance of CrSi2 alloy are discussed in the present paper.

Relationships between Gas-Phase Stoichiometric Ratios and Intermediate Species in High-Temperature Pulverized Coal Flames for Air and Oxy-Fuel Combustions

2012 ◽  
Vol 26 (8) ◽  
pp. 4712-4720 ◽  
Author(s):  
Masayuki Taniguchi ◽  
Yuki Kamikawa ◽  
Tetsuma Tatsumi ◽  
Kenji Yamamoto ◽  
Yuki Kondo
Keyword(s):  
High Temperature ◽  
Gas Phase ◽  
Pulverized Coal ◽  
Intermediate Species ◽  
Stoichiometric Ratios

A Study of Sulfur Reactions in Furnace Deposits

1961 ◽  
Vol 83 (4) ◽  
pp. 444-449 ◽  
Author(s):  
M. Weintraub ◽  
S. Goldberg ◽  
A. A. Orning
Keyword(s):  
Fly Ash ◽  
Liquid Phase ◽  
Flue Gas ◽  
Coal Ash ◽  
Metal Corrosion ◽  
Maximum Absorption ◽  
Boiler Tube ◽  
External Tube ◽  
Sodium And Potassium ◽  
Tube Metal

A study was made of absorption of sulfur from synthetic flue gas by coal ash. When fly ash was placed in a temperature gradient like that in a deposit on a boiler tube, maximum absorption was found in the coldest layer. When held at constant temperature, maximum absorption was found at 1100 F. The amount of absorption was highest for fly ash from furnaces in which serious deposit formation was observed. It was also highest for fly ash containing the highest content of sodium and potassium. The sulfur is probably absorbed as mixtures of normal sulfates, pyrosulfates, and such compounds as potassium-ferric trisulfate. A liquid phase of these compounds in contact with tube metal causes corrosion. The maximum sulfur absorption found at 1100 F coincides with a maximum at the same temperature that has been observed for external tube-metal corrosion.

INFLUENCE OF FORCED CONVECTION IN LIQUID INSIDE THE TIN ON DURATION OF STERILIZATION IN THE COURSE OF FISH PROCESSING

2017 ◽  
pp. 137-144
Author(s):  
Gennadiy Valentinovich Alexeev ◽  
Elena Igorevna Verboloz
Keyword(s):  
High Temperature ◽  
Liquid Phase ◽  
Forced Convection ◽  
Thermal Process ◽  
Processing Time ◽  
Fish Processing ◽  
Study Results ◽  
Equipment Modernization ◽  
Bottom To Top

The article focuses on the process of intensive mixing of liquid phase in the tin during high-temperature sterilization, i.e. sterilization when temperature of the heat carrier reaches 150-160°C. It has been stated that for intensification of the thermal process during sterilization of tinned fish with liquid filling it is preferable to turn a tin from bottom to top. This operation helps to increase the driving power of the process and to shorten warming time. Besides, high-temperature sterilization carried out according to experimental modes, where the number of tin turnovers is calculated, greatly shortens processing time and improves quality of the product. In this case there is no superheating, all tins are evenly heated. The study results will contribute to equipment modernization and to preserving valuable food qualities.

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