锌精矿沸腾焙烧炉埋管综合换热系数的计算与分析

The Calculation and Analysis of the Heat Transfer Coefficient of the Cooling Tube in the Fluidized Roasting Furnace

摘要: 为控制锌精矿焙烧炉床层温度、保障焙烧过程的顺利进行，常采用含水冷的埋管带走锌精矿氧化反应的部分热量，因此埋管面积的合理配置是沸腾焙烧炉结构设计与运行参数优化的关键。它主要取决于焙烧炉产能和综合传热系数，而综合传热系数影响因素多，变化范围大，难以准确获得所需埋管面积，显著延长了焙烧炉生产的调试时间。针对已有的锌精矿沸腾焙烧炉埋管换热系数计算中需假定埋管外壁温度的问题，本文基于埋管稳态传热过程以及传热机理，提出了埋管外壁温度的计算方法，并计算出了不同颗粒粒径和空隙率下的埋管换热系数，结果表明颗粒粒径与空隙率对埋管换热系数影响显著，且锌精矿颗粒粒径越小，影响越大。当颗粒粒径为40 μm、空隙率为0.53时，埋管换热系数可达到1740.28 W/(m²∙K)。

Abstract: In order to control the bed temperature and ensure the smooth process of the zinc concentrate fluidizing roaster, a water-cooled pipe (WCP) is often used to remove a part of the heat from the oxidation reaction of the zinc concentrate. Therefore, it is the key to set the appropriate area of the WCP for the structural design and optimal operating of the boiling roaster. The area of the WCP mainly depends on its comprehensive heat transfer coefficient (CHTC) and the production capacity of the roaster. However, the CHTC has many influencing factors and is of a wide range, which makes it dif-ficult to determine the required area of the WCP. So, people often take a long time to test the running of the roaster. The outer wall temperature was assumed in the present calculating method of the CHTC of the WCP. To improve the accuracy of the CHTC, this paper proposes a method for calculating the outer wall temperature of the WCP, based on the steady-state heat transfer process and mechanism of the WCP. Moreover, the CHTC of the WCP in the case of different particle size and porosity were calculated. The results show that the particle size and porosity have a significant effect on the CHTC, and the smaller the zinc concentrate particle size, the greater the impact. With particle size 40 μm and porosity 0.53, the CHTC can reach 1740.28 W/(m²•K).