煤炭地下气化点火装置燃烧特性数值研究

Numerical Study on Combustion Characteristics of Underground Coal Gasification Ignition Devices

为保障煤炭气化过程安全、稳定,利用气动壅塞原理设计了一种流量准确可控的新型井下“火炬式”点火装置。使用连续管将点火装置送入井下预定位置,注入点火剂和氧气实现自燃引火,着火后持续注入主燃料和空气进行稳定燃烧,进而点燃煤层。利用Fluent软件对该点火装置内部燃烧流场进行了数值模拟,采用了丙烷-空气的两步简化动力学机理和k-ωSST湍流模型进行求解,并对各流场参数分布进行了分析。计算结果表明:设计的离心式气液同轴喷嘴可实现较好的雾化效果,预燃室的内部能够形成稳定的火焰;二次空气补燃配合冷却气帘的设计可以满足加热可燃管、使可燃管可控燃烧,同时降低点火器外壁面温度的要求。研究结果可为煤炭地下气化工作提供参考。

In order to ensure the safety and stability of coal gasification process,a new type of downhole“torch-type”ignition device with accurate and controllable flow rate was designed based on the pneumatic choking principle.Coiled tubing was used to send the ignition device to the predetermined position downhole,and then the ignition agent and oxygen were injected for self-ignition.After that,main fuel and air were injected continuously for stable combustion,and then the coalbed was ignited.Fluent software was used to simulate the combustion flow field in the ignition device.The propane-air two-step simplified kinetic mechanism and k-ωSST turbulence model were used to find the solution,and the parameter distribution of each flow field was analyzed.The calculation results show that the centrifugal gas-liquid coaxial nozzle designed can achieve good atomization,and a stable flame can be formed in the pre-ignition chamber.The secondary air make-up ignition combined with the design of cooling air curtain can meet the requirements of heating the combustible tube,controlling the combustion of the combustible tube,and reducing the temperature of the outer wall of the igniter.The research results in this paper can provide reference for underground coal gasification.