GE conducted engineering and modeling studies to evaluate the feasibility of applying gas reburn technology on Eskom’s Majuba Unit 5 (710 MWe). The key objective of the study was to evaluate the technical and economical feasibility of utilizing a low-calorific fuel gas as a reburn fuel. The fuel gas is produced from an underground gasification process of the Majuba coal deposits, which are difficult to mine. The studies include: (1) develop a conceptual gas reburn injection system that will serve as a basis for the boiler performance impact and economic studies, (2) evaluate mixing performance of the gas reburn system and evaluate impacts of gas reburn on the furnace thermal and species profiles using computational fluid dynamics (CFD) modeling, (3) evaluate impacts of gas reburn on the boiler thermal performance using heat transfer modeling, (4) evaluate NOx reduction potential of the gas reburn systems, and (5) evaluate the economical feasibility of applying gas reburn technology to the Majuba boiler. The study indicates that the proposed reburn fuel and OFA injection systems will provide adequate mixing and reasonable residence time for the reburn application. The potential impacts on boiler performance with injection of the low-calorific fuel gas include the flue gas flow rate, attemperation rate and ID fan capacity. The detailed modeling approach and results are presented in this paper.

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