A novel MILD gasifier for crushed low-grade solid fuels

Abstract

A novel MILD gasifier for crushed low-grade solid fuels is designed and developed to overcome the limitations of conventional packed bed and fluidized bed gasifiers, and the performance parameters of the gasifier are presented in this paper. MILD conditions in the gasifier are created by the velocity differences of the fuel-carrying enriched air jet and off-centred high-speed jets issuing CO2. Crushed high-ash coals and groundnut shells are the two low-grade fuels of particular interest to this study. Gasification of these fuels is performed on the fuel rich side and close to volatiles stoichiometry to enhance the Net CO2 Conversion (NCC), as reported in the earlier studies. Gasification parameters such as the syngas gas composition, fixed carbon conversion, gas calorific value, gasification efficiency, and NCC are evaluated and are compared against the performance of the existing conventional gasifiers. The temperature profile in the gasifier is maintained in the range of 900–1200 ∘C, ensuring self sustained stable ash fusion-free operations. Although, fixed carbon conversion and NCC are observed to be similar to that of conventional gasifiers, the lower calorific value and gasification efficiencies are seen to be lower than the conventional gasifiers. This is attributed to the high heat loss encountered in this laboratory scale MILD reactor. Normalized gasification efficiencies, accounting for the heat loss, is on par with the conventional systems. The latest design has the potential to substitute conventional gasifiers for low-grade powdered solid fuels.