Studying the causes of destruction of steam superheater tubes in boiler equipment

Results of comprehensive studies of samples of prematurely destroyed 57×4 mm steam superheaer tubes of STBA 22 steel used in a boiler unit of Singburi Sugar Co, Ltd factory (Thailand) are presented. The tubes were manufactured at Interpipe Niko Tube Ltd. (Ukraine) according to JIS G 3462 Standard (Japan). They were destroyed in a short (~240 hrs) term of operation. The cause of premature destruction of tubes of the above steel grade and size assortment in the boiler unit has been established. Based on present-day investigation methods (metallography, X-ray diffraction, etc.), it was found that the tubes were operated with violation of fuel combustion conditions and heat-carrying agent circulation. Characteristic features of operation of damaged tubes include high thermal stresses from the side of the fire-chamber and limitation (or absence) of circulation of the heat-carrying agent (blockage in bends, drum heads, etc.). During operation, the tubes were also exposed to significant thermal vibration stresses (unstable combustion conditions). Prolonged overheating occurred at temperatures above 1000 °C because of violation of circulation of heat-carrying agent and unstable combustion mode. High thermal stresses at almost complete absence of a heat-carrying agent, uneven distribution of growing heat flows caused by violation of the combustion mode in the fire-chamber contributed to accelerated degradation of structure and thermal destruction of the tube metal. In a short term of operation (~240 hours), there was a significant change in the tube size (accelerated high-temperature creep) and complete recrystallization of metal structure throughout the entire wall thickness of the damaged tubes. It has been established that the accelerated degradation of metal microstructure in the destroyed tubes was associated with both overheating of the tube wall and the as-delivered metal structure non-recommended for operation at high temperatures and pressures. It was shown that it is necessary to adjust the heat treatment conditions for these tubes at Interpipe Niko Tube Ltd. The study results have made it possible to develop recommendations for eliminating violations of operating conditions and establishing control of actual heat flows in the most thermally loaded sections of the Singburi Sugar Co. Ltd factory’s steam boiler superheater. Taking into account peculiarities of the boiler equipment and its operating conditions, it was also recommended to use a more heat-resistant and refractory steel instead of the currently used material for manufacture of the steam superheater tubes. Keywords: boiler tube, steam superheater, damage, thermal destruction, structure degradation, combustion conditions, heat carrier circulation, overheating.

Comparative Analysis of Models of the Combustion Process of Coal Dust in a Turbulent Flow of a Torch of a Charcoal Boiler

This article provides an overview of existing turbulence models. The scheme of combustion of pulverized coal fuel, the construction of a pulverized coal boiler unit and the process of burning coal in the furnace of a boiler unit BKZ-420-140 are considered. We analyzed the existing turbulence models and selected the most optimal mathematical model to study the combustion process of pulverized coal fuel in order to increase the efficiency of the CHPP.

Statistical approach for analyzing the transient reliability of boiler System using CAS Mathematica

The focal point of this manuscript is to address the reliability analysis of Boiler unit in the Thermal power plant driven from coal. It is made up of six subunits laid out in series and parallel manner, alongwith some standby units. The system under consideration is modelled in transient state aided by Markov birth-death process and CAS Mathematica is deployed to solve the resulting complicated system of probabilistic equations arising out of 8 working states.

EVALUASI PERFORMANCE REGENERASI MIXED BED POLISHER PADA UNIT DEMINERALISASI

One of the important elements produced from the factory support units is air products. Regional water balance (integration) is important to support factory operations. Raw water is treated in the unit section to produce demin water and further process into Boiler Feed Water (BWF) to produce 80 kg/cm2 pressurized steam in the boiler unit, to meet the specifications as demin water it is necessary to carry out several treatments to remove mineral ions (cations and anions) dissolved in the air. In the mixed bed polisher, there is a resin regeneration process to eliminate saturation of the resin which can no longer bind mineral ions. Regeneration or regent is carried out after the resin pile is saturated which is characterized by an increase in product productivity conductivity with the desired product conductivity target of <0.2 μS/cm at a temperature of 25℃. The purpose of this study was to work or perform a mixed bed polisher, especially during regeneration in the demineralization unit. This research was conducted by making a framework of thought and writing work. The writing stage contains data collection, data processing and data analysis-synthesis, as well as drawing conclusions. Based on this research, the results showed that there was a decrease in the performance of the mixed bed with a bed expansion gain of 80.7% and a resin height of 2.42 m. The number of chemicals used for regeneration is 1170.7 kg consisting of HCL and NaOH so that the flow rate of demin water required to dilute the regenerant is 7,126 m3/h. Keywords: Mixed bad Polisher, Demin water, Resin regeneration.