Causes of damage to baffle pipes in high-pressure drum boilers at the Ust’-Ilimsk heat and electric power plant

Abstract

The causes of damage to the baffle pipes in BKZ-420-140PT-2 high-pressure drum boilers during combustion of Irsha-Borodin and Zheronskii coals are analyzed. Damage to the salt module pipes was caused by the buildup of internal sediments and untimely chemical washing of the baffles. Flaws and bulging of the clean module pipes in the constriction region are caused by insufficient flow velocities in the 76/62-mm diameter pipes and high thermal loads during burning of Zheronskii coal. The fundamental solution for increasing the reliability of the boilers is to rebuild them with conversion to dry slag removal.Seven BKZ-420-140PT-2 boilers manufactured at the Barnaul Boiler Factory are in use at the Ust'-Ilimsk heat and electric power plant of the JSC "Irkutskénergo." These single drum boilers with liquid slag removal, natural circulation, and compensated draft, have a steam production of 420 tons/h, design pressure of 140 kgf/cm 2 , and superheat temperature of 560°C. They are designed for burning Irsha-Borodin brown coal from the Kansk-Achinsk Basin. The boiler has a Ð-shaped configuration and a gas-tight construction.The furnace chamber is completely baffled by all-welded membrane panels and is separated by a constriction of the pipes in the back and front baffles into two parts: the combustion chamber and the cooling chamber. The panels that form the corner boundary of the combustion chamber and the upper declivity of the constriction for a length of 0.7 m are made of 76/62 mm diameter pipes. The upper declivity of the constriction is not studded and does not have heat resistant grease. The combustion chamber is made in the form of two octagonal preliminary chambers joined by a corridor. The back baffle pipes form a slightly inclined hearth in which there are two tap holes for slag removal. The walls of the preliminary chambers are studded and heated. Slit flowthrough burners are mounted at the corner faces of the preliminary chambers (for burners in each preliminary chamber). The axes of the burners in each preliminary chamber are oriented tangentially to an imaginary circle of diameter 1000 mm. Eight overflow burners are mounted above the main burners on the same corner panels of a preliminary chamber.The cooling chamber is in the shape of a prism. Its lower part is formed by the pipes from the upper declivity of the constriction, directed at an angle of 60°to the horizontal. The crown of the furnace is shielded by the pipes of the front baffle. Every fifth pipe in the back baffle forms a scallop which is positioned at the inlet to the horizontal gas duct. The other pipes shield the hearth of the horizontal gas duct and form a scallop at the inlet from the horizontal gas duct, and along the crown the horizontal gas ducts pass into collectors which are common to all the pipes in the back baffle.The evaporation scheme in the boiler is two-stage, with washing of the steam by feed water. The first stage is directly connected to the 1.6-m-diameter drum, located at elevation 37.3 m along the boiler front. 67 in-drum du...

Reliability Analysis Based on Fault Tree of Failure of Boiler Drum

“…However, this method lacks comprehensive consideration on the overall drum [1]; Yan Sicong etc. have put forward a new kind of method called probability fatigue failure analysis.Provided theinitial fatigue quality is known, the result that its fatigue reliability analysis model predicts is relatively ideal and has high accuracy [2]. Other methods, such as IC method, first-order second-moment methodand Monte Carlo method, require a large amount of data to support [3].…”