The Flow Numerical Simulation And Structural Optimization Of Pulverized Coal Oxygen-Rich Ignition

A lot of fuel oil was needed in the boiler's operating process to complete cold condition ignition and low-load stable combustion. With the price of fuel oil rising, developing less-oil or oil-free ignition technology to reduce oil consumption in the boiler's ignition and low-load combustion becomes imminent in recent years.Based on strengthening temperature and oxygen provision which are the main control parameters in the pulverized coal ignition and combustion process, high temperature oxygen-enriched oil-free pulverized coal ignition technology was proposed and the relational oil-free pulverized coal ignition device--pulverized coal oxygen-enriched ignition was designed in this paper. The pulverized coal oxygen-enriched ignition was designed to two parts to reduce the oxygen consumption. The first-part was ignited by high-temperature oxygen firstly in the process of pulverized coal oxygen-enriched ignition, and the whole ignition was completed by igniting the second-part of pulverized coal oxygen-enriched ignition using high-temperature torch of the first-part oxygen-enriched combustion.The basic structure dimensions and work parameters of pulverized coal oxygen-enriched ignition were identified firstly by detailed calculation and analysis, and numerical simulation on flow field of pulverized coal oxygen-enriched ignition was carried out by FLUENT software and the relational structure optimization was achieved in this paper. The studies indicated that organize the flow field effectively in the first stage ignition process to form a larger and reasonable shape recirculation region is the guarantee of intensive mixing of pulverized coal flow and high-temperature oxygen and the key for success ignition. The optimization about the first stage of the oxygen-enriched coal igniter shows that In stable operating conditions, select the taper with a length of 30 mm and vertex angle 60 degree as the guiding cone and place the cone at the position 0mm from the primary pulverized coal exports, the half angle of center tube nozzle's flaring select 15 degree, the half angle of high- temperature oxygen swirling jet's flaring select 25 degree, the igniter get the best recirculation region in this structure. In the conditions of same structural parameters, when the recirculation region high-temperature oxygen swirl intensity select 1.5 to 2.5, and the speed of pulverized coal flow in the center tube is between 12.5m/s and 20m/s, the igniter get the best recirculation region. It is easy to get fire as long as the second-stage pulverized coal and air flow smoothly into first-stage recirculation zone formed by the high temperature oxygen and have enough oxygen to support the second stage of the igniter. The results of overall optimization of igniter are as follow: Under the same operating parameters, the optimization is best when half angle of over-fire air swirling jet's flaring select 20 degree. In the case of the same structural parameters, the best over-fire swirling intensity is 2.5, the best air and pulverized coal velocity is between 15m/s and 25m/s.