High-pressure Steam Boilers Research Articles

Failure investigation of a water-wall tube of fossil-fuel fired boiler

Failure investigation of water tube failure in boilers, especially in thermal power stations, is of paramount importance because it plays a crucial role in supplying energy to the dependent processing units in refineries. The failure investigation of the water-wall tube at the roof position in a boiler is presented in this work. In order to identify the root cause of the rupture, various destructive and non-destructive analyses were performed at multiple locations on the failed tubes. Visual inspection revealed a fish mouth-type rupture opening with excessive wall thinning about 60% before its failure and a diametrical growth of up to 150 % from the nominal diameter at the bulge location.From the chemical composition analysis, mechanical testing, and hardness measurements, the material was found to meet the requirement of SA 210 Grade A standards. This is a typical steel grade for high-pressure and temperature systems widely used in boilers. The microscopic examination revealed that the structure of the sound part of the tubes consisted of ferrite and pearlite structures. Whereas the microstructure of the bulged area exhibited a partial decomposition of the pearlite colonies, as well as formations of bainitic structures indicates localized overheating beyond the lower critical temperature (Ac1) of 723 °C for phase transformation. The absence of significant internal deposits and multiple bulges, ductile mode of failure, spheroidization in the ferrite matrix, and violent rupture are indications of short-term overheating. The failure mechanism of localized short-term overheating is identified as a result of the flame impingement due to the burner misalignment. A rupture of a tube in a high-pressure steam boiler can be catastrophic. A proper root cause analysis of the failure provides insight into the operating window for process variables, the interval of tracking feed water quality, and a planned shutdown inspection to avert any unpredictable shutdown in high-temperature applications. Understanding boiler-tube failures may improve stream-generating equipment performance, safety, availability, and reliability.

Deaerator system pressure and liquid level PID regulation control strategy

Excessive oxygen content in the feed water of industrial boilers will cause oxidative corrosion on the metal surface, resulting in grooves or even thinning of the metal tube wall, resulting in trachoma until it is completely damaged. Therefore, the quality of the deoxidation effect greatly impacts the service life of industrial boilers and directly affects the economic benefits of enterprises. Automatic equipment and PID parameter adjustment are used to improve the deoxygenation performance of the deaerator system, making the oxygen content of the water in the industry meet the standard, thereby reducing the oxidation and corrosion of pipelines and prolonging the practical life of the equipment. This article mainly introduces Shanxi Yaxin Energy Group Co., Ltd. and Xinneng Technology Co., Ltd. 's 220-ton CDQ coke oven with co-production 120T SS98 high-temperature and high-pressure steam boiler, supporting a set of XNC-130 deaerator produced by Lianyungang Huagang Power Equipment Co., Ltd., the design output is 130t/h, the working pressure is 0.03MPa, the working temperature is 104℃, the design pressure is 0.3MPa, the design temperature is 120℃, the water tank volume is 50m³, and the material Q345R. The system uses Siemens PLC, Rosemount pressure transmitter, regulating valve and other equipment combined with PID control algorithm to achieve pressure and liquid level adjustment and the best deaeration effect.

Ethylene Yield from Pyrolysis Cracking in Olefin Plant Utilizing Regression Analysis

Ethylene yield is significant in showing the performance of the steam cracker furnace in the olefin plant. This study was conducted in the actual large-scale olefin plant to see the impact of various variables towards the ethylene yield. The analysis was conducted utilizing Regression Analysis in Minitab Software Version 18 to develop a reliable ethylene yield model. The model concluded that ethylene yield in the studied plant was contributed by the factor of -0.000901, 0.02649, -0.282, 0.16, -0.0834, 0.1268, and 0.0057 of Hearth Burner Flow, Integral Burner Flow, Steam Drum Pressure, Super High-Pressure Steam (SHP) Boiler Feed Water Flow, SHP Flow, Naphtha Feed Flow, and Stack NOx Emission respectively. The Response Optimizer tool also showed that the ethylene yield from naphtha liquid feed utilizing pyrolysis cracking can be maximized at 32.55% with control setting at 9,476.41 kg/hr of Hearth Burner Flow, 608.56 kg/hr of Integral Burner Flow, 112.93 Barg of Steam Drum Pressure, 109.11 t/hr of SHP Boiler Feed Water Flow, 86.42 t/hr of SHP Flow, 63.49 t/hr of Naphtha Feed Flow and 126.23 mg/m3 of Stack NOx Emission.

The evaluation of corrosion rate of steel during chemical cleaning of steam boilers

Traditional and new washing acid reagents are used for chemical cleaning of internal surfaces of steam-water pipes of boilers. In previous studies, the rate of removal of lumpy and uniform deposits in the evaporative pipes of high-pressure steam boilers depending on the type of cleaning solution and the duration of cleaning was obtained. However, during chemical cleaning, removing deposits is accompanied by corrosion processes of the metal pipes, which leads to their loss. In the scientific and technical literature there are practically no data characterizing this process when using new detergent reagents. The aim of the study is to obtain experimental data on the corrosion rate of steels during the acid stage of chemical cleaning with the use of new cleaning reagents such as Antirzhavin, Deskam and Auge Pro AC 60. The gravimetric method of determination of metal corrosion rate of evaporative pipes is used. The samples of corrosion in cold and heated washing solutions during chemical cleaning from deposits by etching are employed. The laboratory testing has revealed the dependences of corrosion rate of carbon steel of boiler evaporative pipes and corrosion indicating plates in heated and not heated washing solutions of the inhibited hydrochloric acid and acid reagents on cleaning duration. It has been found that the corrosion rates of carbon steel are reduced during the cleaning process and at the end of the acid stage in solutions of inhibited hydrochloric acid and reagent solutions have values exceeding the maximum permissible corrosion rate in a cold inhibited technical solution of hydrochloric acid. However, they are less than those for pure metal and metal with scale. The experimental data obtained can be used in the selection of a chemical reagent for acid cleaning and its optimal duration, as well as in the selection of the method of steel corrosion control during cleaning.

Determining of kinetic characteristics of chemical cleaning from scale deposits in steam boiler generating tubes

Reliable operation of steam boilers is maintained by periodic in-service cleanings of the internal surfaces of the steam-water path. Such cleanings can be made with traditional and new acid cleaning agents. The nec-essary condition for developing an effective chemical cleaning program is predicting its required duration taking into account the properties of the detergent used and the contamination of the metal surface. Insufficient duration of this operation leads to increased residual contamination, while excessive duration – to metal dissolution. Traditionally, the required time for chemical cleaning is evaluated according to the results of laboratory experiments. The aim of this study is to obtain analytical dependencies and characteristics describing the kinetics of the acid stage of steam boiler chemical cleaning. The laboratory studies of the acid stage of chemical cleaning of samples of high-pressure steam boiler generating tubes were performed by the chemical etching method. The rates and completeness of the removal of lumpy and uniform deposits by acid reagents were also determined. The method of mathematical modeling was used to obtain the kinetic equation. The conditional purification rate constants for this equation were found by the methods of statistical processing of laboratory results. A description of the scale removal rate from the inner surface of the steam generating tubes is proposed as a first-order kinetic equation depending on their specific contamination and reagent washing solution acidity. The equation allows calculating the required duration of chemical cleaning for providing a given value of specific residual contamination of the metal surface. According to the results of the laboratory studies, the conditional rate constants of purification were determined using proven detergent reagents and types of scale. The adequacy of the obtained results is ensured by their consistency with real-life data. The results of the study can be used to select the technology of acid stages of chemical cleaning of lumpy and uniform deposits and justify their duration for providing standard values of specific residual contamination of the surface of steam generating tubes of drum boilers.

Application of the Energy Approach to the Evaluation of the Serviceability of the Drum of a Steam Boiler Subjected to Thermal Cycling and Hydrogenation

We develop a method for the evaluation of the influence of hydrogen on the strength and durability of the drum of a high-pressure steam boiler subjected to thermal cycling and hydrogenation. We analyze the influence of hydrogen on the accumulation of damage to the metal and the duration of operation of the drum for different modes of damage. It is established that hydrogen accelerates the accumulation of damage and reduces the period of operation of metals by 25–30% for planned shutdowns of the boilers and by 40–50% for their emergency shutdowns.

Advances in electrodeionization technology for ionic separation - A review

Electrodeionization (EDI), which combines electrodialysis (ED) and conventional ion-exchange (IX), is a mature process which has been applied since more than twenty years on commercial use for the production of ultrapure water (UPW). Eliminating chemical regeneration is the main reason for its commercial success. The increase in acceptance of EDI technology has led to an installation of very large plant as the commercial state of the art that produces <TEX>$1,500m^3/h$</TEX> of water for high pressure steam boiler. More recently, EDI system has found a number of new interesting applications in wastewater treatment, biotechnology industry, and other potential field. Along with further growth and wider applications, the development of stack construction and configuration are also become a concern. In this paper, the principle of EDI process is described and its recent developments, commercial scale, and various applications are pointed out.

Study of Improvement in Boiler Efficiency through Incorporation of Additional Bank of Tubes in the Economiser

The major efficiency loss of a boiler is caused by the hot stack gases discharging to the atmosphere which is polluting the atmosphere and on other side Pollution Control Board is forcing the norms of Pollution levels in atmosphere. One of the most cost-effective ways of improving the efficiency of a high pressure steam boiler is to install an economizer on the boiler. An economizer is a heat exchanger, which transfers heat from the stack gases to the incoming feedwater. Typically, on a high pressure water tube boiler, the efficiency improvement with an economizer is 2 to 4%, depending on firing rate. On a high pressure fire tube boiler, the improvement is 2 to 3.5%, depending on boiler size and firing rate. The economizers are located in the boiler stack close to the stack gas outlet of the boiler. They may be supported from overhead or from the floor. A feedwater line, which serves the boiler, is piped to the unit. No additional feedwater control valves or stack gas dampers are required. Presently in NTPC stage II units there are banks of tubes in economizer. There was a proposal from management to add another bank of tubes in the economizer so that there will be control of pollutants coming out from boiler. We took that proposal as a task and made a detailed investigation of it. An investigation is conducted on the effect of performance of the boiler by incorporating the additional bank of tubes in the space below the lower bank of tubes. The main idea is to extract maximum amount of heat from the flue gases and increase the heat pick up rate of the feed water outlet into the boiler. By assuming the additional bank of tubes, various heat transfer calculations are done and the reduction in the flue gas out let temperature and increase in the feedwater outlet temperature are found out. Finally a comparison of efficiencies of the boiler is made between the existing unit and the unit when additional bank of tubes are assumed. At last, various pros and cons have been found out by conducting above investigation i.e. by incorporating additional bank of tubes in the economizer.

Effect of hydrogen on corrosion damage of metal of the high-pressure energetic boiler drum

The causes and mechanism of initiation and growth of pointed and linear pits, separations and cracks of corrosion origin on the internal surface of the shell of high-pressure ( 15.5 MPa ) steam boilers used at heat power plants were investigated by the LLMS, SEM, AES, SIMS and fractography methods. It was found as a result of comprehensive investigations that initiation and growth of the above damages were caused by hydrogenation and embrittlement of metal in the zones resulting from the simultaneous effect of an unfavourable local combination of several factors, such as formation of regions with a quenching structure and structural heterogeneity in the joining zone between dissimilar metals, many years of thermal cycling and corresponding thermal fatigue, local variations in chemical composition of metal in the intergranular and interface regions between the phases and corresponding variations in mechanical properties of given microvolumes of metal with a decreased crack resistance against the background of an increased sulphur content and decarburized surface layer of metal on the steam boiler drum shell.

Features of brittle damages and hydrogen impregnation of high-pressure boiler tube metal

A significant number of failures encountered in high-pressure steam boilers of thermal electric power stations are caused by damage of the tubes of the steam superheaters, which are made of 20, 12Kh1MF, 12Kh2MFSR and 12Kh18N10T steels. A statistical analysis made by the authors determined that a large number of the failures result from the action of hydrogen on the tubes. In this paper, the mechanisms of hydrogen diffusion, corrosion crack propagation, and brittle failure for steam superheater tubes were analyzed. Hydrogen-related intergranular cracking and thermal fatigue were assessed for the tube steels. It was concluded that hydrogen had a significant effect on processes of crack origin and propagation both in the superheater and in the unheated tubes of the boilers.

The service life of steam boiler drums

The occurrence of cracks in steam boilers made in the Federal Republic of Germany, the Soviet Union and the German Democratic Republic led to a detailed investigation of the state of steam boiler drums in Czechoslovakia, and to an analysis of the computing methods used in operation. The properties of the material—particularly resistance to high-cycle fatigue, low-cycle fatigue and thermal fatigue—were studied on 15223 (cf ASTM A302) steel, a grade which is most frequently used in Czechoslovakia for the production of high-pressure steam boiler drums. This made it possible to plot a limit fatigue life for boiler drums made from this steel.

Atomic Power Engineering under Falsified Safety Standards

In July 1970 the United States Department of Justice accused the American Society of Mechanical Engineers (ASME) of violating the Sherman Antitrust Act and of acting in restraint of trade by restricting the ASME Certificate of Authorization and the use of the Code Symbol Stamps to boilers and pressure vessels manufactured in the United States and Canada. During the succeeding two years attorneys for the parties in the case formulated a Consent Decree without a public confrontation in the Court. Furthermore, the membership of ASME was kept uninformed until October of 1972, after the Consent and Final Judgment had become effective and new procedures had been developed for allowing foreign manufacturers to apply the ASME Code Symbol Stamps to their products. As a consequence, a breakdown in engineered safety standards has been sanctioned and this is undermining the engineering profession's overriding responsibility to protect the public health and safety. This breakdown of professional responsibility is especially serious in the new technology of atomic power. American insurance companies, which have traditionally written 100% insurance coverage for property damage and third party liability against explosions of high pressure steam boilers bearing the ASME Code Stamp, have refused to write such insurance coverage on nuclear reactors. In the author's opinion there is evidence that the Consent was formulated under collusive proceedings and he calls on the members and the Council of ASME to appeal for dismissal of the Consent Decree.

Lining fireboxes in a high-pressure steam boiler

The service conditions of the lining in high-pressure steam boilers with gas turbine blowing are characterized by a heating temperature above 1500–1550°C on the working surface and repeated sharp changes in temperature at rates of up to 100 deg/min during heating and up to 85 deg/min during cooling. In these conditions it is advisable to use silicon carbide refractories which are the most heat-resistant.

Forced Outage Rates of High-Pressure Steam Turbines and Boilers

Forced Outage Rates of High-Pressure Steam Turbines and Boilers

Forced Outage Rates of High-Pressure Steam Turbines and Boilers [includes discussion

Forced Outage Rates of High-Pressure Steam Turbines and Boilers [includes discussion

Discussion: “The Behavior of Sodium Sulphite in High-Pressure Steam Boilers” (Hitchens, R. M., and Purssell, Jr., J. W., 1938, Trans. ASME, 60, pp. 469–473)

Discussion: “The Behavior of Sodium Sulphite in High-Pressure Steam Boilers” (Hitchens, R. M., and Purssell, Jr., J. W., 1938, Trans. ASME, 60, pp. 469–473)

Closure to “Discussions of ‘The Behavior of Sodium Sulphite in High-Pressure Steam Boilers’” (1939, Trans. ASME, 61, p. 269)

Closure to “Discussions of ‘The Behavior of Sodium Sulphite in High-Pressure Steam Boilers’” (1939, Trans. ASME, 61, p. 269)

Discussion: “The Behavior of Sodium Sulphite in High-Pressure Steam Boilers” (Hitchens, R. M., and Purssell, Jr., J. W., 1938, Trans. ASME, 60, pp. 469–473)

Discussion: “The Behavior of Sodium Sulphite in High-Pressure Steam Boilers” (Hitchens, R. M., and Purssell, Jr., J. W., 1938, Trans. ASME, 60, pp. 469–473)

The Behavior of Sodium Sulphite in High-Pressure Steam Boilers

Abstract 1 Tests for sulphite and sulphite in condensed steam and for sulphide in boiler water are described, which tests are sensitive to 0.01 ppm as sulphur. 2 By these tests, it was found that no hydrolysis of sodium sulphite occurs up to a boiler pressure of 1775 lb per sq in. 3 Tests on water in boilers operating at 675 and 1400 lb per sq in. pressure showed no auto-oxidation and reduction of sodium sulphite in such waters. Tests on a third boiler, carrying a pressure of 1775 lb per sq in., showed slight traces of such a reaction. The slowness of sulphite consumption in the three boilers precludes any significant auto-oxidation and reduction at the metal surfaces. This is opposed to certain laboratory data which indicate that this reaction is of the first order and rapid at high temperatures. 4 Of the small amounts of sodium sulphite carried into the steam mechanically, a portion decomposes to sulphate and sulphide as the spray of water becomes concentrated or dried. The amounts present, however, are too small to be of significance. 5 In view of these findings, it is the authors’ conclusion that sodium sulphite can be used in high-pressure boilers with no harmful effects. 6 A continuous feed to maintain 10 to 20 ppm sodium sulphite in the boiler water is recommended.

Carbonaceous Zeolites—An Advance in Boiler-Feedwater Conditioning

Abstract The increased number of modern high-pressure steam boilers emphasizes the need for high-quality feedwater make-up of minimum scale-forming and minimum total-solids content consistent with the desired sulphate-carbonate ratio. The usual sodium zeolites hitherto known, which exchange their sodium base for calcium and magnesium (hardness), reduce this hardness to a minimum, but do not reduce total solids or alkalinity. The new hydrogen zeolites described in this paper retain the simplicity and complete hardness-removal characteristics of zeolite softeners and at the same time eliminate the alkalinity with (a) a corresponding reduction in total solids and CO2 content of steam, and (b) an increase in the sulphate-carbonate ratio. Furthermore, they remove alkalinity present in any form; thus, for the first time in history it is possible, by simple economical means, to remove sodium alkalinity often found in raw waters. When the capacity of these hydrogen zeolites is exhausted, they are regenerated by dilute acid solutions in the same manner as a salt solution is used to regenerate sodium-zeolite softeners. By combining the hydrogen- and sodium-zeolite effluents in correct proportions, or by alkali neutralization, it is a simple matter to obtain a feedwater completely free from hardness and of any predetermined desired alkalinity. These hydrogen zeolites are made of carbonaceous substances and are therefore practically free from silica. They can also be regenerated with common salt, and with such regeneration they can function in the usual sodium-zeolite cycle. Being extremely resistant to low pH waters and practically free from silica, and of relatively high capacity, they also possess great advantages when used in the usual sodium-zeolite cycle, especially where it is desired to avoid any increase in silica content, a condition that is gaining favor rapidly in the high-pressure-boiler feedwater field.