Investigation of the Gasification Performance of Lignite Feedstock and the Injection Design of a Cross-Type Two-Stage Gasifier

In the last three years, the Institute of Nuclear Energy Research (INER) has been developing the E-GAS gasification numerical model and analyzing the gasification performance by conducting several parametric studies. A preliminary numerical model considering coal particles tracking, two-step volatiles thermal cracking, and nine chemical reactions has been established. In last year's results, the single lateral injector design in the second stage of E-GAS gasifier is found nonideal for the gasification process. Therefore, one of the objectives in this study is to modify the second stage injection and investigate its effect on gasification performance. Moreover, because of rising interest in the use of low-rank coals as the feedstock for power plants, the second goal in this paper is to investigate the gasification features by using North Dakota (ND) lignite as the feedstock. The result shows that a dual-injector design (either tangential or opposing jets) in the second stage injection of E-GAS gasifier can minimize the nonideal recirculation zone and improve the gasification performance. Furthermore, a tangential injection design can make the average temperature reach equilibrium more quickly, so the height of the E-GAS gasifier could therefore be shortened. Moreover, by examining the energy needed for the second stage injection, a tangential injection design saves more energy as compared to the opposing-jets design. The result of the assessment of ND lignite shows that under the same condition of O-2/coal and coal/slurry ratios, no matter what the feedstock flow rate or the total input heating value, the gasification performance of ND lignite is always lower than that of Illinois #6 coal. However, the cheaper price of ND lignite makes it more competitive, and if the electricity generating industries can accept a lower gasification performance, the usage of ND lignite can be a choice to be considered.