Investigation into Operation of a Semitower Boiler of a 158-MW Power Unit and Prospects for Application of Such Boilers in Russia

Abstract

Steam boilers of various arrangements (or profiles) exist in the world. The most widely used ones include, for example, semitower boilers (or L-paso boilers). In Russia, there is not sufficient experience in designing such boilers, especially in their practical application. The paper analyzes advantages and disadvantages of semitower boilers. As with tower boilers, their main advantage is a small footprint. However, compared to tower boilers, the L-paso boilers have a lower height. According to the performed analysis, the semitower configuration is best suited to boilers fired with gaseous or liquid fuel. In Russia, due to its climatic conditions, semitower boilers can be used for replacements of obsolete (type E) natural circulation gas-and-fuel oil-fired boilers with a steam output of 210–420 t/h. As an example, the paper presents a brief description of the L‑paso (type Ep) natural circulation reheat boiler manufactured by the well-known Babcock–Wilcox Co. This boiler, which is a part of a 158-MW power unit, has been successfully fired with sulfur fuel oil for many years. A customized numerical model of the boiler was developed in the Boiler Designer software package. Multivariant calculations of the boiler were performed on the basis of this model. An analysis of the predictions has confirmed that the boiler can operate in a wide range of loads while maintaining the design steam conditions. The furnace heat release rate q_F, the furnace cross-section heat release rate q_V, and the flue gas temperature at the furnace outlet \(\vartheta _{{\text{f}}}^{{''}}\) have been demonstrated to considerably exceed the values allowed by the applicable Russian regulations for similar boilers. This fact is explained. The gas velocities in the boiler gas ducts are noticeably higher, and the gas and air velocities in the air heater are approximately the same as in the Russian-made boilers. The steam enthalpy increments Δh and the mass velocity ρw in the superheater stages basically correspond to the concepts of Russian specialists.