Investigation of Heat Transfer and Gasification of Two Different Fuel Injectors in an Entrained Flow Coal Gasifier

One of the problems frequently encountered in a coal gasifier operation is fuel injector failure. Operating in extreme high pressure and high temperature, the typical fuel injector life span is 6–12 months. Numerical simulations are performed to study the flow and temperature fields in the vicinity of the injector tip and the metal temperature of two different fuel injector designs—one with a conical-nozzle tip and the other with a blunt tip—in a dry-fed, entrained-flow coal gasifier. The complete 3D Navier–Stokes equations are solved. The instantaneous gasification model is employed to simulate three global heterogeneous reactions and three homogeneous reactions, including volatile combustion. The results show that the two different injectors give very different temperature and species distributions inside the gasifier. In the gasifier with the conical injector tip, the highest temperature inside the gasifier occurs at the center of the gasifier, whereas in the gasifier with the blunt-tip injector, the highest temperature occurs near the wall. There is a potential of flash-back combustion in the nozzle at the tip of the conical injector due to its premixing feature of fuel and oxidant in the nozzle. The highest temperatures on both injectors are the same, which is around 1600 K. However, the highest temperature on the conical-tip injector is concentrated at one location with an extended region of 30 mm between 1600 K and 1100 K, whereas on the blunt-tip injector, hot spots are scattered and the hot region (1600–1100 K) only extends about 3 mm. Experimental results support the simulated results and has demonstrated a short life of the conical-tip fuel injector and much extended life for the blunt-tip fuel injector.