城市污水污泥燃烧特性和动力学特性分析

采用热重分析仪对城市污水污泥进行热重实验，通过TG(热重)、DTG(微分热重)和DSC(差示扫描量热)曲线的分析对比，获得污水污泥热解和燃烧不同阶段的特性。低于250℃，燃烧与热解的热重曲线基本吻合，说明在此之前，失重速率主要受控于有机物的分解以及析出，燃烧过程对失重影响不明显。燃烧DTG曲线呈现“W”峰型，第一个失重速率峰与热解DTG曲线基本对应，高于410℃，燃烧DTG曲线出现显著的加速。采用Coats-Redfern 积分法，假设不同的反应模型进行拟合，推断出污泥燃烧过程中两个DTG峰体现出不同的反应机理。借鉴煤燃烧机理分析认为，污泥燃烧反应初期挥发分的燃烧受控于化学反应速率，随着温度的不断提高，剩余挥发分的燃尽和固定碳的燃烧总反应速率逐渐受扩散因素控制。基于分析所得污泥燃烧机理，采用四个独立的平行反应模型模拟污泥的燃烧过程，拟合曲线与实验数据吻合良好。

Combustion behavior and kinetic characteristics of a city sewage sludge

The pyrolysis and combustion characteristics of a city swage sludge were studied by analysing the TG, DTG and DSC curves from a thermogravimetry. The combustion and pyrolysis TG curves are similar before 250℃, suggesting that the loss rate of weight is controlled mainly by the decomposition of organic matter, and the action of combustion is less. The DTG curve of combustion presents a “W” shape peak, the first peak is in a good agreement with the pyrolysis DTG curve. The weight loss rate has a rapid acceleration after 410℃. Based on the Coats-Redfern integral method, some reaction models are tested to fit the combustion process, and the results show that the burning process with two DTG peaks has a complicated mechanism. It can be concluded that the volatile burning in the initial combustion stage is controlled by the chemical reaction rate, while with the rising of temperature the combustion rate of the residual volatile and fixed carbon is controlled gradually by the diffusion. According to the mechanism, a four-parallel reactions model is brought out to simulate the burning process, which better fits the experimental data.