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Research Papers

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

[+] Author and Article Information
Ting Wang

Energy Conversion and Conservation Center, University of New Orleans, 2000 Lakeshore Drive, New Orleans, LA 70148-2220twang@uno.edu

Armin Silaen

Energy Conversion and Conservation Center, University of New Orleans, 2000 Lakeshore Drive, New Orleans, LA 70148-2220asilaen@uno.edu

Heng-Wen Hsu

 Energy and Enviromental Laboratory, Industrial Technology Research Institute Building, 64, 195, Section 4, Chung Hsing Road, Chutung, Hsinchu, Taiwan 310, R.O.Chsuhw@itri.org.tw

Cheng-Hsien Shen

 Energy and Enviromental Laboratory, Industrial Technology Research Institute Building, 64, 195, Section 4, Chung Hsing Road, Chutung, Hsinchu, Taiwan 310, R.O.Cchshen@itri.org.tw

J. Thermal Sci. Eng. Appl 2(1), 011001 (Jul 06, 2010) (10 pages) doi:10.1115/1.4001806 History: Received February 12, 2010; Revised May 11, 2010; Published July 06, 2010; Online July 06, 2010

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.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the original fuel injector design (scale: mm)

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Figure 2

Schematic of the new fuel injector design (scale: mm)

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Figure 3

Meshed computational domain for the entire gasifier (3 m high and 0.15 m in diameter) with the original injector design (Case 1)

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Figure 4

Meshed computational domain for heat transfer simulation within the original fuel injector (Case 1)

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Figure 5

Meshed computational domain for fluid mechanics and reactions simulation inside the gasifier for the modified injector design (Case 2)

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Figure 6

Meshed calculation domain for heat transfer simulation within the modified design fuel injector (Case 2)

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Figure 7

Temperature and species distributions on the horizontal plane at the injector height for Case 1

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Figure 8

Temperature distribution on the injector outside surface and its surrounding flow for Case 1 seen from two opposite sides

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Figure 9

Temperature distribution on the horizontal and vertical center planes of the injector for Case 1

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Figure 10

Temperature distribution on the injector outside wall for Case 1

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Figure 11

Temperature and species distributions on horizontal plane on injector height for Case 2

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Figure 12

Velocity vectors and temperature distributions on the horizontal plane on the injector height for Case 2

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Figure 13

Temperature distribution on outside wall of injector for Case 2

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Figure 14

Temperature distribution on the horizontal and vertical center planes of the injector for Case 2

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Figure 15

Exterior wall of the gasifier using fuel injectors with premixed fuel nozzles. Red spot indicates heat penetration through worn-out brick caused by premixed flash back combustion in the nozzle.

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Figure 16

Burned out converging-tip fuel injectors

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Figure 17

The right blunt-tip injector shows it is in mint condition after a short service and the left injector shows a burned-out tip after extended service

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