Abstract

In this study, wet air with ash particles was used to simulate real dryer exhaust from lignite-drying process, and its ash deposition characteristics along horizontal tube bundles were experimentally studied to provide theoretical guidance for the design and operation of waste heat recovery devices. The ash deposition on the longitudinal section of the tube bundles was considered, and the ash deposition thickness under different experimental conditions was quantitatively measured using digital imaging techniques. The spatial and temporal distributions of the ash deposition thickness and its variation with mainstream inlet temperature, mainstream velocity, water vapor mass fraction, and ash particle concentration were presented. The ash accumulated on the windward side of the tube bundles and mainly concentrated on the first five rows in the inlet section, especially on the first two rows. The rapid growth of ash deposition mainly occurred in the first 3000 s and then gradually stabilized. The ash deposition thickness was insensitive to the mainstream inlet temperature and velocity, whereas the water vapor mass fraction and ash particle concentration had significant influences on the ash deposition thickness. When the water vapor mass fraction increased from 5% to 15%, the average ash deposition thickness decreased from 7.67 mm to 1.87 mm. As the ash particle concentration increased from 1.0 g·m⁻³ to 14.8 g·m⁻³, the average ash deposition thickness increased from 1.91 mm to 26.0 mm. The change in ash deposition thickness was significantly larger than that in heat transfer coefficient under different conditions.

摘要

本研究采用带灰粒的湿空气模拟褐煤干燥过程中的实际干燥机排气，并对其沿水平管束的灰分沉积特性进行了实验研究，为余热回收装置的设计和运行提供理论指导。考虑管束纵向截面上的积灰，利用数字成像技术定量测量不同实验条件下的积灰厚度。给出了灰沉积厚度的时空分布及其随主流入口温度、主流流速、水蒸气质量分数和灰颗粒浓度的变化。灰烬堆积在管束的迎风面，主要集中在进气段的前五排，尤其是前两排。灰分沉积的快速增长主要发生在前 3000 s，然后逐渐趋于稳定。灰沉积厚度对主流入口温度和速度不敏感，而水蒸气质量分数和灰颗粒浓度对灰沉积厚度有显着影响。当水蒸气质量分数从 5% 增加到 15% 时，平均灰分沉积厚度从 7.67 mm 减小到 1.87 mm。随着灰分颗粒浓度从 1.0 g·m 增加 灰沉积厚度对主流入口温度和速度不敏感，而水蒸气质量分数和灰颗粒浓度对灰沉积厚度有显着影响。当水蒸气质量分数从 5% 增加到 15% 时，平均灰分沉积厚度从 7.67 mm 减小到 1.87 mm。随着灰分颗粒浓度从 1.0 g·m 增加 灰沉积厚度对主流入口温度和速度不敏感，而水蒸气质量分数和灰颗粒浓度对灰沉积厚度有显着影响。当水蒸气质量分数从 5% 增加到 15% 时，平均灰分沉积厚度从 7.67 mm 减小到 1.87 mm。随着灰分颗粒浓度从 1.0 g·m 增加^-3到 14.8 g·m ^-3，平均灰分沉积厚度从 1.91 mm 增加到 26.0 mm。不同条件下灰沉厚度的变化明显大于传热系数的变化。