Numerical investigation of high-temperature rapid heating of coal gas in CFB heat exchanger via thermal carrier particles

Abstract

High-temperature rapid heating technology of coal gas is a crucial issue that urgently needs to be addressed for the recycling of coal gas in the iron manufacturing. Drawing upon circulating fluidized bed principles, this study proposed a high-temperature rapid heating technology of coal gas with employing thermal carrier particles. Numerical simulation studies were conducted to evaluate the heating performance of this method. A 3D grid model was established and the Discrete Particle Model (DPM) was employed to simulate the gas-solid two-phase flow and heat transfer behaviors in the riser. The results demonstrate that the gas-solid flow within the circulating fluidized bed (CFB) heat exchanger is capable of achieving rapid heat transfer. The gas was effectively heated from an inlet temperature of 300 K to 1479 K within a height of 4.2 m and within 0.68 s. The CFB heat exchanger achieves rapid heat transfer under the designed industrial operating load conditions, with an average duration of heat exchange not exceeding 1.34 s. Moreover, the axial and radial particle size distribution was investigated during the gas-solid heat transfer process in the CFB heat exchanger and analyze the relationship between particle size distribution and the velocity and temperature of particles. To evaluate the operational flexibility of the riser, the gas-solid two-phase flow patterns, temperature distribution and particle residence time distribution were examined under different operating loads.