Studies Of Experiment And Simulation Of Cold Mild Gasification Technology

As one of the key technologies to develop the clean coal technology with high efficiency and low pollution, coal gasification technology has many different forms which are limited to its special applications and coal types and most of them use high temperature slag tapping. The high temperature of gasification furnace can contribute to the reaction rate, improve carbon conversion efficiency and promote the discharge of liquid slag, at the same time it will cost additional coal combustion to maintain high temperature which make the rise of specific oxygen uptake rate and carbon dioxide concentration, and it is hard for high ash melting coal to operating temperature higher than the melting temperature of the ash under a smooth and efficient gasification. Therefore, based on mild combustion technology advantages and the realization approaches of flameless oxidation, this thesis will aim at the design of a new dry feeding entrained flow bed gasification nozzle to realize the mild coal gasification under ash melting temperature and improve calorific value of gas and carbon conversion rate through adjusting different [O]/[C] atom ratio and steam/coal ratio.The key point of mild combustion theory lies in the high flue gas reflux ratio which caused by the high speed of fuel and oxidizer. The strong recirculation exhaust gas preheat reactants and diluted and mixed with reactants which will make a high temperature and low oxygen concentration. The combustion reaction speed is reduced and reactant spread the whole furnace chamber and the combustion peak temperature is reduced which lead to the reduced formation of NOX and CO. In order to realize coal mild gasification based on mild combustion theory, author main work is as follows:(1) For purpose of providing a reliable and stable continuous coal conveying scheme in the experiment of coal mil combustion and gasification, we build a pulverized coal pneumatic conveying equipment and make a detailed analysis of the top discharge blow tank low flow rate in dense phase pneumatic conveying characteristics for pulverized coal.(2) Building a small vertical organic glass model furnace and study and observe the changes of cold state field of the pulverized coal in furnace by different nozzle arrangement and outlet types to provide an intuitive cognition and reference for numerical simulation and hot-state experiment.(3) Studying the changes of cold state flow field organization in coal furnace by numerical simulation based on different nozzle size and symmetry and eccentric arrangement.(4) Building a thermal experimental facility and achieve a stable ignition of pulverized coal and coal mild combustion, realize coal mild gasification by an optimized nozzle structure, adjusting [O]/[C] atom ratio and steam/coal ratio and obtain a higher calorific value gas and carbon conversion rate.Finally, on the basis of mild combustion (flameless oxidation) approaches, we realize the goal of air and water vapor as gasification agent coal mild entrained flow gasification at normal temperature and atmospheric pressure, and achieve a better calorific value gas and carbon conversion rate as [O]/[C] of 1.05 and steam/coal ratio of 0.1kg/kg, respectively 3.59MJ/Nm3 and 72.4%.