Energy and Exergy Investigations of a Separated-Gasification Chemical Looping Combustion-Combined Cycle System for Power Production

Abstract

The concept of a novel separated-gasification chemical looping combustion (SG-CLC) system, which is mainly composed of a bubbling fluidized bed as the gasification reactor, a fast fluidized bed as the reduction reactor (RR), and a counter-flow moving bed as the air reactor (AR), has been proposed and evaluated through our previous subpilot scale unit. Extending from the previous work, the present study aims to further investigate the feasibility and potential of this technique for power production. A comprehensive steady-state model integrating various unit blocks has been developed to simulate the operation process of a megawatt-class SG-CLC-combined cycle system based on the ASPEN PLUS simulator. A Chinese Shenhua bituminous coal is used as the fuel with a Fe-based oxygen carrier. During the simulation, the net power production, energy efficiency and exergy efficiency of the combined cycle system, and the work duties of different components are obtained. In addition, the effects of some important operating variables on the system power production performance are elucidated in-depth. The results have shown that the electricity production performance is closely related to the upstream SG-CLC combustion system. At an input thermal power of 1.1 MW and a water flow rate of 750 kg/h, the energy efficiency and exergy efficiency of this novel SG-CLC-combined cycle system can reach high values at 42.9 and 35.6%, respectively. In addition, higher power generation efficiencies can be achieved by properly decreasing the flow rate of feed water, or increasing the temperatures of the RR and the AR.

Fast versus turbulent fluidization of Geldart Group B particles

“…The red horizontal line represents the median, the upper and lower boundaries of the box represent respectively the 75th and 25th percentiles, and the upper and lower whiskers extend to the most extreme data points within 1.5 times the difference between the 75th and 25th percentiles from the box boundaries. The left column corresponds to 1188 datasets from a fast fluidized bed, 16,17 while the right column corresponds to 378 datasets from a turbulent fluidized bed 20 [Color figure can be viewed at wileyonlinelibrary.com]…”

“…Random Forest out‐of‐bag permuted predictor importance estimates for local cluster characteristics. The left column corresponds to 1188 datasets from a fast fluidized bed, 16,17,25 while the right column corresponds to 378 datasets from a turbulent fluidized bed 20 [Color figure can be viewed at wileyonlinelibrary.com]…”

“…The fast fluidization regime is operated as a circulating fluidized bed due to the much higher entrainment rates 9 . This regime similarly garners much interest in applications similar to that of the turbulent bed like carbon capture, 19 combustion, 20 chemical synthesis, 21 and biomass gasification 22 . In contrast to the turbulent fluidized bed in which only the gas flow is controlled, both the gas and solid flows are controlled in the fast fluidized bed.…”