Study on Gas-Solid Flow Characteristics of Loop Seal Surge in Circulating Fluidized Bed Boiler

Jul 6, 2026

Upload by Skyler

A low-frequency loop seal surge during operation of a 350 MWe supercritical circulating fluidized bed (CFB) boiler can cause cracking in the castable material of the internal insulation layer, threatening normal and safe boiler operation. A computational particle fluid dynamics (CPFD) study analyzes the surge causes, relevant parameters, and elimination conditions. Results indicate that under surge conditions the pressure-drop gradient exceeds 3526 Pa/m and downcomer material flow becomes non-smooth, while loop-seal particle volume fraction is too low for effective sealing. By keeping primary fluidized air, supply air, and recycle air within defined limits, surge can be prevented.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages12

Reading Time30 min

Introduction

Circulating fluidized bed combustion and boiler relevance

Need for numerical simulation

CFD and CPFD approaches

Contents lists available at ScienceDirect Chemical Engineering and Processing - Process Intensification journal [homepage: www.elsevier.com/locate/cep](homepage: www.elsevier.com/locate/cep) | Study on gas-solid flow characteristics of loop seal surge in circulating fluidized bed boiler | | | | | --- | --- | --- | --- | | Xin Shena,* , Xiaoqian Lia, Hairui Yang b, Yan Jinc<br>a College of Intelligent Manufacturing Engineering, Shanxi Institute of Science and Technology, Jincheng, 048000, China b Department of Energy and Power Engineering, Tsinghua University, Haidian District, Beijing, 100084, China c College of Electrical and Power Engineering, Taiyuan University of Technology, Taiyuan, 030024, China | | | | | A R T I C L E I N F O | | A B S T R A C T | | | Keywords: CPFD method CFB boiler Loop seal Surge<br>Gas-solid flow | | During the operation of a 350 MWe supercritical circulating fluidized bed (CFB) boiler, a low-frequency surge in the loop seal can lead to cracks in the castable material of the internal insulation layer, thereby impacting normal and safe boiler operation. Using the computational particle fluid dynamics (CPFD) method, the effect of a lowfrequency loop seal surge on the gas-solid flow of a 350 MWe supercritical CFB boiler was studied in this paper. The causes, parameters and elimination conditions of the loop seal surge were analysed. The results show that when the loop seal is under a surge condition, the pressure drop gradient is greater than the critical material sealing value of 3526 Pa/m, and the material flow in the downcomer is not smooth. The volume fraction of material particles in the loop seal is low, which cannot effectively seal the material. When the primary fluidized air, supply air, and recycle air are controlled within a reasonable range, the loop seal surge can be effectively prevented. The acceptable range for primary fluidized air is 14.5 m/s to 16.0 m/s; for supply air, it is 0.05 m/s to 0.10 m/s; and for recycle air, it is 1.0 m/s to 1.5 m/s. | | 1. Introduction Circulating fluidized bed (CFB) combustion is a clean coal technology that has developed rapidly in recent years [1]. CFB boilers are characterized by wide fuel adaptability and are particularly suitable for China’s complex coal types and large reserves of inferior coal [2]. In the past thirty years, circulating fluidized bed combustion technology has developed rapidly in China. By the end of 2020, China had placed >480 large CFB boilers into operation, with a total installed capacity of nearly 90 million kilowatts [3,4]. Although the current primary models of large CFB boilers are 135 MWe and 300 MWe, the proportion of supercritical units has exceeded 7 %. It is anticipated that in the future, with the continued operation of a significant number of supercritical CFB units, they will become the new primary model [5]. At present, two 660 MWe, one 600 MWe and fifty-four 350 MWe supercritical circulating fluidized bed boilers have been placed into commercial operation in China, among which 350 MWe supercritical circulating fluidized bed boilers are the most widely used. For industrial-grade circulating fluidized bed boilers, gas-solid flow characteristics are the foundation of pollutant generation and combustion heat transfer and have important research value and significance. However, conducting experiments on these boilers has several drawbacks, including high research costs and limited data acquisition. The proposed dynamic flow similarity criteria make it possible to scale down hydrodynamics of a large-scale CFB boiler [6,7]. Despite advancements in measurement tools and research methods due to the progress of science and technology, many crucial parameters in furnaces remain challenging to measure through experimentation or are subject to certain limitations. With the rapid advancement of computer technology, numerical simulations of gas-solid flow and optimized combustion in industrial boilers have be

FAQs

What operational problem does the loop seal surge cause in a supercritical CFB boiler?

A low-frequency loop seal surge can lead to cracks in the castable material of the internal insulation layer, impacting normal and safe boiler operation.

How was the loop seal surge impact on gas-solid flow studied?

The study used the computational particle fluid dynamics (CPFD) method to analyze effects of low-frequency loop seal surge on the 350 MWe supercritical CFB boiler.

What parameter ranges can effectively prevent loop seal surge?

Primary fluidized air should be 14.5–16.0 m/s, supply air 0.05–0.10 m/s, and recycle air 1.0–1.5 m/s.

Jul 6, 2026

Upload by Skyler